The word "rational" comes from the Latin roots meaning able to reason. Reasoning is just the manner of thinking that we do when we think logically. For example, you might think: "I generally hate any kind of oatmeal. This food is oatmeal. Well, therefore, I likely will hate this food." This is a rational or logical way of thinking.

When something is "mature," it is fully developed. Sometimes, the word is used to describe food that has become ripe; however, it can also be used to describe someone's personality. For example, a mature adult is someone who takes life seriously, as is appropriate for someone of his or her age. An immature person is someone who is not mature. Thus, the best option among those provided here is "childish."

When someone is "reluctant," he or she hesitates to do some given task. For example, we could say, "Because of her fear of spiders, Courtney was reluctant to enter the old house for fear of finding many of the insects in it." This means that Courtney did not want to enter the house and likely hesitated because of her fears.

The word "insane" is used to describe someone or something that is crazy. For instance, a person who has lost his or her mind would be called "insane". Such a person requires a lot of care to keep himself or herself safe. An "insane idea" is a crazy one. For example, if someone told you that they were going to try to use a pig as a parachute when jumping out of a plane, you could say that the person had an "insane idea." 

When we say that something is "agreeable," we are saying that it is enjoyable (or at least not unenjoyable). For this question, the correct answer is a synonym for the way that we say something like, "He had an agreeable personality."  This means that the person had a personality that was on the whole friendly and enjoyable. In a way, you could say that most people would agree to be around such a person!

When someone is a "fanatic," he or she intensely follows some way of life. For example, a person might be a fanatic for exercise, meaning that he or she does a lot of exercising. Sometimes, fanatics are dangerous people, as when someone supports a political cause and wants to hurt people; however, "fanatical" does not always have to describe such dangerous characters. It can just describe someone who is very energetic—enthusiastic—for a cause. This is the best answer among those given.

The word "tender" is not "tinder," which is a small kind of wood used for building a fire. Instead, to be "tender" means that you are kind. You could say, "Bill was very tender to his wife, showing her much affection after a stressful day of work."  Thus, "kind" is the best option given.

When someone is "assertive," he or she is very confident. This can come off as being arrogant because such a person can be a little pushy, but the primary meaning of assertiveness is the character trait of being confident. Therefore, the best option is simply "confident." Do not be tricked by "conceited" or "arrogant". These are trap options!

When someone is "attentive," he or she is very aware of his or her surroundings. Therefore, "attentive" can mean merely to be very aware. None of the options exactly match this meaning, but a secondary meaning of "attentive" is "to be thoughtfully aware of others." This is clearly related to the first meaning, though it is a little more focused. Therefore, the best option is "thoughtful," as this expresses at least the second meaning of "attentive."

The word "responsible" can mean guilty, as when we say, "He was responsible for the crime." Someone can also be "responsible for himself or herself." Whenever we grow up, we become more "responsible," meaning that people can rely on us to do what we say we are going to do. An immature person is not yet responsible. A mature person is. Hence, "mature" is good synonym for "responsible." This has nothing to do with age. It has everything to do with a good character. You're only young once, but you can immature forever!