What is this passage mainly about? (Drinking the Fog)
Read an Informational Passage · ELPAC Grades 3–5 reading. The correct answer, and the reasoning behind it.
A longer factual text, with questions about the main idea, supporting details and vocabulary.
Read the passage. Then answer the questions.
Drinking the Fog
Coast redwoods are the tallest trees in the world. Some grow more than 300 feet high. A tree that tall has a problem. Water is heavy, and pulling it from the roots all the way to the top takes a great deal of work.
Along the northern California coast, thick fog rolls in from the ocean on summer mornings. The fog drifts through the redwood branches and collects on the needles. Drops form, join together, and fall to the forest floor like light rain. Scientists have measured this. In some forests, fog drip supplies as much as a third of the water the trees receive in a year.
The trees also drink from above. Redwood needles can take in water straight from the fog, so the top of the tree does not have to wait for water sent up from the roots.
The fog helps other living things too. Ferns, banana slugs and young redwood seedlings all depend on the damp ground the fog leaves behind. Drier summers mean less fog, and less fog means a thirstier forest.
The question
Choose the best answer.
What is this passage mainly about?
- Redwoods are the tallest trees in the world.
- Fog is an important source of water for redwood forests.Correct answer
- Banana slugs live on the floor of the forest.
- Scientists measure the rain that falls in California.
Why “Fog is an important source of water for redwood forests.” is correct
A main-idea question asks what holds the whole passage together, not which fact is most interesting. Every paragraph here returns to the same point: fog brings water to the redwood forest and to the things living in it. A useful test is to ask whether a choice covers all four paragraphs or only one sentence.
Why the other answers are wrong
- Redwoods are the tallest trees in the world. — This is the passage's opening fact and sets up the problem, but the passage then goes on to explain something else.
- Banana slugs live on the floor of the forest. — Banana slugs are one example in the final paragraph, far too small a detail to be the main idea.
- Scientists measure the rain that falls in California. — The passage mentions measuring fog drip, not rainfall, and only in a single sentence.
Practice more of this
More reading practice for Grades 3–5, or see the ELPAC practice test for grades 3–5. For other grades, see free ELPAC practice tests by grade.
This is an independent study resource. It is not affiliated with, endorsed by, or connected to the California Department of Education or the official ELPAC program. All questions here are original practice material written to match the published task formats.