The word "attentive" is used to describe someone who is carefully aware of something. It means that he or she gives that thing his or her attention. To be attentive does not necessarily mean that such a person is intelligent; however, it does mean that he or she is aware. Thus, we would say, "She was an attentive listener, never missing a single word said to her."

Do not confuse "thorough" with "through!" The word "thorough" means complete or total. It is used to describe something that is not done merely partially but is done in its fullness. For example, if you clean your room "thoroughly," you have done so completely.

Whenever something is "accessible," we can get to it relatively easily. An "accessible building" is one that doesn't take a lot of complicated maneuvers to reach. An "accessible item" on a shelf can be grabbed without a lot of trouble. "Accessible" does not mean "short" or "tiny"—even if being short or tiny makes some things more accessible. Instead, this question uses a secondary meaning of "accessible." We can also say that ideas are accessible. Thus, if someone can explain things in an understandable manner, we say that he or she is very accessible in his or her talking.

When something is "intricate," it is complex. Thus, we can say, "He gave an intricate answer, taking a long time to describe all of the details of the new building." Also, you could say that a new invention is intricate if it is made up of many parts that fit together in complex ways. Therefore, the best option among those given is "complicated."

"Convoluted" means something is unclear or easy to understand, therefore, "complicated" would be the word most like convoluted.