Correct Answer: to have detailed knowledge of something

Solution : The correct answer is the third option.

Explanation : The idiom know like the back of one's hand, is used to express a high level of familiarity or detailed knowledge about a particular thing. In this case, the phrase like the back of one's hand is a simile, emphasising the idea that someone knows something as well as they know the back of their own hand. It implies a deep understanding or awareness of a subject, object, or situation.