Maybe you have heard of "toxic waste" or "toxic chemicals." The word "toxic" describes something that is not healthy but, instead, is poisonous. This is not the same as being "murderous," but it is the same as being "deadly." "Deadly" things are dangerous and harmful—as are toxic ones. "Toxins" are things that are harmful (or toxic) in this way.

Whenever two things are distinct, they are different from each other and cannot be confused with each other.  For example, we could say, "Those two character traits are distinct.  Some people can be angry without turning red."  This means that turning red is something different than being angry.  The best option among those provided is "separate", for this communicates the idea of being two distinct realities.

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.  

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."

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.

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

"Gorgeous" means beautiful.

"Conspicuous" means standing out so as to be clearly visible. "Noticeable," which means able to be easily noticed, is the best synonym of "conspicuous," so "noticeable" is the correct answer.

Incorrect answers:

"Invisible" means not able to be seen. It is an antonym of "conspicuous," which means clearly visible, so it is incorrect.

"Ordinary" means having no special or unusual features or normal, as in the sentence, "My house looks ordinary and doesn't stand out among the other houses in my neighborhood."

"Terrifying" means causing a feeling of extreme fear, as in the sentence, "I have a fear of heights, so while I thought that the Grand Canyon was beautiful from a distance, I found it terrifying when I stood at the edge and looked down."

"Visible" means able to be seen. The best choice is "noticeable," which means able to be noticed. Something that is "noticeable" can be seen. Considering the other choices, "permeable" means full of small holes so certain things may pass through, "cloudy" means not clear, and "vision" is sight. Even though "vision" is related to "visible," it is a noun while "visible" is an adjective. Since "noticeable" is both close in definition to "visible" and an adjective, it is the best choice.