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

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One paper per pupil

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Set 1 has all 25 in a single PDF. 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.

The Accidental Photograph

In 1895 Wilhelm Röntgen was working with a covered tube in a darkened room when he noticed a screen across the laboratory glowing. Something was passing through the cover and crossing the room. He did not know what it was, so he called it X — the unknown. He spent seven weeks alone in the laboratory testing it. He put wood, rubber and metal in the way. Metal stopped it; the rest did not. Then he asked his wife to put her hand between the tube and a photographic plate. The picture showed the bones of her hand and her wedding ring. Within a year, X-rays were being used in hospitals. Röntgen refused to patent them.

  1. 1. Explain the relationship between the seven weeks of testing and the photograph of the hand.

LessonPrint · RI.4.3 · Set 16 · free to copy for classroom use

Answer key — What Happened and Why

Set 16. 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. The testing established that metal stopped the rays and other materials did not, which is what made the bone photograph possible.

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.