A punctuation question with an -ing phrase tests how the phrase connects to the sentence around it. Read both sides and find who or what does what, then ask whether the phrase adds extra information you can cross out. An -ing word needs a helper such as is to say what its subject does. A semicolon joins full sentences, a comma attaches extra information, and no mark attaches words the main sentence needs. With and, the joined parts must have matching forms.
Hints
- Hint 1
Look at what the boardwalk does before the blank. Does that part become a full sentence once the place name is filled in?
- Hint 2
Read through the words about observing wildlife and look for a main verb that lets them stand alone.
- Hint 3
Cross out the words about observing wildlife. Does the description of the boardwalk's route still work as a full sentence without them?
Step-by-step
Test and attach the final phrase
Step 1Check the boardwalk's sentence
The park's boardwalk zigzags gives us a subject, boardwalk, and a main verb, zigzags, which says what that subject does. To choose the punctuation, let's test whether the words on each side can stand alone. Does the first part work once we add marsh? Yes: it tells us where the boardwalk goes and how far, so the first part is a full sentence.
- Step 2
Test the words about visitors
Does the phrase about observing wildlife have a main verb of its own? It starts with allowing, an -ing word with no helping verb such as is, and visitors to observe contains no main verb either. No main verb appears later, so the phrase can't stand alone. Cross it out, and the route is still fully described, which shows that the phrase adds extra information about what the boardwalk makes possible.
- Step 3
Attach the extra information
How do we attach extra information that ends with along the way? One comma opens it, and the sentence's ending closes it, so marsh allowing leaves out the needed mark. The semicolon in marsh; allowing needs a full sentence afterward, while marsh, and allowing joins zigzags to allowing, which aren't matching verb forms. The version marsh, allowing uses the one comma needed to set off the phrase. Choice B.