Answer:
The answer to your question would be that the sentence that corrects the dangling modifier in the sample sentence is the following one: After reading the whole book, I found that the ending was unsatisfying.
Step-by-step explanation:
Dangling modifers occur when the subject being modified, or described by the modifier, does not actually appear in the sentence. As the modifier has no subject in these sentences, it is said to be "dangling". The fact is that modifiers should be placed as closely to the element they are modifying. For instance, the first sentence makes it look as if the ending was the one reading the whole book. As this is impossible, you need to correct the sentence. This is done by including a subject and making sure that the modifier goes directly after the subject it is modifying, just as the revised version of the sentence shows.