A question about word order and end marks tests whether a sentence asks or tells you something. Read the words leading into the blank and decide whether a question is being asked. A yes-or-no question puts a verb before its subject, the person or thing the sentence is about, and ends with a question mark. A statement keeps the subject first and ends with a period. Check both features together, because smooth wording doesn't tell you whether the sentence follows that pattern.
Hints
- Hint 1
Read from “researchers observed” to the comma, and look at how the blank is introduced. Is the sentence asking the reader something or telling the reader what the researchers found?
- Hint 2
Set the phrase about scarce water aside for a moment. How would you continue after “researchers observed that” and end the whole sentence?
Step-by-step
Match word order and end mark
Step 1Decide whether the sentence asks or reports
The words researchers observed that introduce the blank as something the researchers found during their study. Does that make the whole sentence a question or a statement? It tells us what they found rather than asking us anything, so the sentence needs a period.
- Step 2
Read past the phrase about water
What does when water becomes scarce add to that statement? It tells us when the finding applies, and the comma closes that part. The words after the comma still complete what the researchers observed, so they need statement word order: the subject, who or what does something, comes before its verb.
- Step 3
Apply both rules to the blank
To complete what the researchers observed, put plants, the subject, before close, the verb telling what they do. Do plants close instead puts do before plants, which is direct question order. The version with plants close and a period gives us statement word order and the right end mark. Choice C.