Which of the following sentences contains a dangling modifier?
a. walking through the woods, we could see there were animals everywhere.
b. opening the door, we could see that the room was very large.
c. looking through the window, the room seemed very large.
d. none of these

The correct answer is C. Looking through the window, the room seemed very large.

Here, the dangling modifier is looking through the window. A dangling modifier is a modifier that is either incorrectly placed in a sentence or doesn't refer to anything. The correct revision of this sentence would be Looking through the window, we saw that the room seemed very large because then the modifier would refer to the subject, which is lacking in the original sentence. The way it was written, it would seem that the room was looking through the window. 

The correct answer should be D. none of these

All of the modifiers used in the sentences are correctly placed and don't provide ambiguity.