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Following a Chain of Causes is a free printable Grade 4 English worksheet on holding a multi-step causal chain together, aligned to Common Core standard RI.4.10. It prints 2 questions with an answer key on its own sheet of paper, in 25 versions that each ask 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.

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Set 1 has all 25 in a single PDF. All 25 sets ask different questions.

Following a Chain of Causes

RI.4.10

NameDate

Read the text, then answer the questions.

1.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.
  2. 2. Put these in order: penicillin reaches soldiers, Fleming publishes, Florey and Chain read the paper.
  3. 3. Summarise this text.
2.Read the text, then answer the questions.

The Wolves and the Rivers

Wolves were shot out of Yellowstone by 1926. Fourteen were brought back in 1995. With no wolves, elk had grazed the valleys freely for seventy years. Young willow and aspen were eaten as soon as they grew. The wolves killed some elk. More importantly, they changed where elk would stand still. Open valley floors became dangerous, so the elk stopped lingering there. Willow and aspen grew back along the rivers. Beavers, which need willow, returned. Their dams made ponds. Roots held the banks. The rivers narrowed, deepened and moved less. Some researchers describe this as wolves changing the shape of rivers, though others argue the effect has been overstated.

  1. 1. Explain the relationship between the wolves and the shape of the rivers.
  2. 2. Summarise this text.
  3. 3. Put these in order: beavers return, wolves are reintroduced, willow grows back.

LessonPrint · RI.4.10 · Set 19 · free to copy for classroom use

Answer key — Following a Chain of Causes

Set 19. Prints on its own sheet.

  1. 1.1. They read the paper ten years later and took on the problem Fleming had not solved: producing penicillin in quantity. 2. Fleming publishes, Florey and Chain read the paper, penicillin reaches soldiers. 3. Fleming spotted mould killing bacteria in 1928 and published to no response; Florey and Chain solved the production problem, and by 1944 penicillin reached soldiers.
  2. 2.1. Wolves made valley floors dangerous, so elk moved on, willow grew, beavers returned and dammed, and roots held the banks. 2. Wolves returned to Yellowstone in 1995, changed where elk grazed, allowed willow and beavers back, and are credited — with some dispute — with reshaping the rivers. 3. Wolves are reintroduced, willow grows back, beavers return.

Last reviewed 2026-09-05. Aligned to RI.4.10 of the Common Core State Standards for English language arts.