A punctuation question with the same word in every choice tests how sentence parts fit together. Read around the blank and name the parts that meet there. A preposition links its object, a noun or phrase, to other words. Then check each punctuation form: commas separate items or set off extra information, dashes mark a break or explanation, and colons introduce something after a full sentence. No mark is needed between directly linked words, such as a preposition and its object.
Hints
- Hint 1
Read only through the word supplied at the blank, and check whether that stretch can stand alone. Does it still need the words after the blank to finish its meaning?
- Hint 2
Focus on the word before the time phrase. What does “Saturday morning” complete, and do those two parts belong together?
Step-by-step
Find the words that belong together
Step 1Test the colon
Read Caroline is signing up volunteers for the neighborhood cleanup through the word each choice supplies, since we're testing punctuation after that word. Can a colon follow that stretch? A colon needs a full sentence before it, but stopping at the blank leaves us waiting for the time that follows. That rules out the version with a colon.
- Step 2
Name the two parts
What does Saturday morning complete? It finishes the linking word supplied at the blank, telling us when the cleanup will happen. That linking word is a preposition, and the word or phrase that completes a preposition is called its object. So the time phrase is the preposition's object, not a separate comment.
- Step 3
Leave the preposition attached
No punctuation goes between a preposition and its object, so the version with a comma and the version with a dash split words that belong together. The version with on and no mark lets Saturday morning complete the preposition directly. Choice D.