An apostrophe question tests whether you can tell when a noun owns something and how many owners there are. Read past the blank and test for ownership by asking whether the next thing belongs to the noun. Then count the owners in the passage, not the things owned. One owner takes 's; plural owners ending in s take an apostrophe after it; other plurals take 's. Wrong forms can sound right while changing the number of owners or losing ownership.
Hints
- Hint 1
Read past the blank to responses. Ask whose responses are being described.
- Hint 2
Look back at the noun naming the group. Does that noun name one person or several, and does its plural form end in s?
Step-by-step
Test ownership, then count the owners
Step 1Test for ownership
The phrase the immune response of children tells us whose responses are being compared, and the blank comes before responses. Does the noun in the blank own that next noun? Try the of test: the responses of the children says what the sentence means, so the responses belong to the group named in the blank. The noun needs an apostrophe to show that relationship.
- Step 2
Count the people, not the responses
Now count the people who have the responses, not the responses themselves. Does children name one person or several? It names more than one child, so the owners are plural, and child's changes the sentence to describe the responses of only one child. Don't use the plural responses to decide how many owners there are: one child could have several responses, but the earlier noun tells us this sentence is about a group.
- Step 3
Use the ending for this plural
Does the plural itself end in s? The passage's children is already the plural of child, so adding another s would create childrens, which isn't a word. A plural owner without a final s takes 's; a plural owner already ending in s takes an apostrophe after that existing letter. The form childrens' puts an apostrophe after the s of that made-up plural, but children's keeps the word plural and adds the ending that shows whose responses they are. Choice D.