The reason for choosing "give in" as the correct phrasal verb in the sentence is as follows:

1. Give in : This phrasal verb means to surrender, yield, or comply with someone's request or demand. When you "give in" to someone's demand, you essentially agree to do what they are asking, often because of pressure, persuasion, or the circumstances.

In the context of the sentence, it conveys that the police did not yield or comply with the kidnapper's demand, indicating a refusal to fulfill the demand. This is the appropriate choice to express the idea that the police did not succumb to the pressure or demands of the kidnapper.