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What Happened and Why is a free printable Grade 4 English worksheet on explaining an event using the text's own information, aligned to Common Core standard RI.4.3. It prints 2 questions with an answer key on its own sheet of paper, in 25 versions, 19 of them with different questions, so no two pupils in the class work from the same page. Print it from the browser or download it as a PDF — no account, no email.

Set 1 of 25 · the same problems every time you open this link.

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19 of these 25 sets ask different questions — this skill does not have 25 questions to give. The rest reorder them, so no two pupils have the same paper in front of them.

What Happened and Why

RI.4.3

NameDate

Read the text, then answer the questions.

1.Read the text, then answer the questions.

Lichen

A lichen is not one organism. It is a fungus and an alga living as one body. The fungus provides the structure and holds water. The alga photosynthesises and makes sugar. Separated, the fungus starves and the alga dries out. Because it needs no soil, a lichen can grow on bare rock, on gravestones and on the roofs of cars that have not moved for a decade. Lichens grow extremely slowly — some crustose species less than a millimetre a year. Scientists use that rate to date rock surfaces, a method called lichenometry. Lichens also absorb whatever is in the air. Where the air is dirty, they disappear, which makes them a living measure of pollution.

  1. 1. Explain the relationship between the fungus and the alga.
2.Read the text, then answer the questions.

How Penicillin Was Found

In 1928 Alexander Fleming went on holiday and left a stack of dishes on a bench. Each held a colony of bacteria. When he came back, one dish had a spot of mould on it. Around the mould was a clear ring where the bacteria had died. Fleming realised the mould was producing something that killed bacteria. He named it penicillin and published a paper. Almost nobody noticed. Ten years later, Howard Florey and Ernst Chain read that paper and tried to make penicillin in quantity. That turned out to be the hard part: it took two thousand litres of mould fluid to treat one patient. By 1944 the problem had been solved and penicillin was reaching soldiers in the field.

  1. 1. Explain the relationship between Fleming's paper and Florey and Chain's work.

LessonPrint · RI.4.3 · Set 1 · free to copy for classroom use

Answer key — What Happened and Why

Set 1. Prints on its own sheet.

  1. 1.1. The fungus gives structure and water, the alga makes sugar; separated, the fungus starves and the alga dries out.
  2. 2.1. They read the paper ten years later and took on the problem Fleming had not solved: producing penicillin in quantity.

Questions about What Happened and Why

What does the What Happened and Why worksheet cover?

It practises explaining an event using the text's own information — 2 questions for Grade 4, all on Common Core RI.4.3: Explain what happened and why, using the text's own information. The instruction to pupils is “Read the text, then answer the questions”, and the answer key follows on the next sheet.

Which Common Core standard does What Happened and Why practise?

CCSS.ELA-LITERACY.RI.4.3 — RI.4.3, in the Reading: Informational Text domain for Grade 4. The published standard reads: “Explain events, procedures, ideas, or concepts in a historical, scientific, or technical text, including what happened and why, based on specific information in the text.” The worksheet assesses that standard rather than a paraphrase of it.

What age or grade is this worksheet for?

What Happened and Why is written for Grade 4, typically ages 9-10. It is one of the sheets on RI.4.3, so it suits any pupil working at that standard — including older pupils revisiting it and younger ones working ahead.

Does What Happened and Why come with an answer key?

Yes. All 2 answers are generated from the same problems as the questions, so the key cannot drift out of step with the sheet. It starts on a fresh sheet of paper, after the questions, so it is not handed out with the class by accident.

How many different versions of What Happened and Why can I print?

25 versions, of which 19 ask genuinely different questions — this skill does not have 25 distinct questions to give, so the rest reorder them and no two pupils still share a paper. Set 1 downloads all 25 as one PDF.

Is What Happened and Why free to print and photocopy?

Yes. What Happened and Why, its answer key and its 25 versions are free to print and photocopy for your own class, with no account, no email capture and no subscription at the download step. Please do not resell them or republish them as your own.

Is there a lesson plan to teach RI.4.3?

Yes — “Explaining Events, Procedures and Ideas” is a 40-minute Grade 4 plan for RI.4.3, timed section by section, with the misconceptions to expect and an exit ticket. What Happened and Why is the practice that follows it.

More practice for RI.4.3

Explain what happened and why, using the text's own information.

Teaching this next? Explaining Events, Procedures and Ideas is the 40-minute plan for it, with the misconceptions to expect.

All Grade 4 worksheets

Last reviewed 2026-09-05. Aligned to RI.4.3 of the Common Core State Standards for English language arts.