C) The bookshelves swayed with the weight of their load.
A dangling modifier is a description that seems to be connected to the wrong noun grammatically. Sometimes they are hard to spot since our brains make the connection for us, but if you read the sentence exactly as it is, you will notice it. Option A is wrong because the modifier is "feeling anxious", but we don't know who or what is feeling anxious. Our brains know that it is the person who is having to hold still, but there is no person in the sentence. Option B is not correct because the modifier "screaming" is close to the noun "raft" in the sentence. We know that a raft cannot scream therefore the modifier is not in the right place. Option D's modifier is "missing my family". In the sentence the modifier seems to be modifying dormitory, but this doesn't make sense since a dormitory doesn't have a family or the capability to miss one.