All of the related words in this question describe how something is informational or helpful with regard to knowledge. Something may be said to be illuminating not only if it produces physical light, but also if it “shines light (intellectually) on a topic." The same pertains to the word “enlightening.” Something “scholarly” is not necessarily enlightening. Indeed, merely to be scholarly means that it befits a scholar. The thing in question could merely be part of the unhelpful debates that sometimes occur among academic personalities. Likewise, something scholarly could be very difficult to understand because of its attention to obscure details, perhaps burying the main insight under a mountain of facts.

Each of the related words here is concerned with being “relevant,” that is, being related to a matter being considered. Something is “pertinent” when it “pertains” to a question or situation. For instance, if someone insists on asking questions that really are not related to a lecture, a teacher has full rights to say, “Your question is not pertinent, and I will ignore it. Even though it is interesting, it will just distract us from our main topic.” Something “germane” is likewise relevant, and while “fitting” might seem to be used more in the sense of physically “fitting” (as in clothes), the term has this meaning precisely because “to be fit” means to be of suitable status or quality. Something “extraneous” is irrelevant and outside the bounds of a given topic or matter.

All of the words here pertain to some kind of communication; however, note that the group of related words describe particularly communicative, expressive, and understandable types of communication. Something “enunciated” is expressed in a clear manner. (The word is related to “announce.” Imagine something clearly “announced” and—hence—known). An "articulate" person is one who can communicate in a very clear manner. The word "article" actually comes from the word for small joint or piece. An articulate person is able to present things “at the joints”—in small but understandable portions. A "lucid" presentation is one that “casts light” on a subject, making it intelligible. Someone who is "eloquent" is well spoken, having excellent and persuasive style. In such a company of expressive and able words, “spoken” is quite a weak adjective in comparison!

This set of words is a bit strange, but given that both “opaque” and “translucent” are found among the options, let us realize that it must have something to do with how light passes through a surface. The other three words all relate to the state of being soiled or dirty, indicating that in such a case there would be little light that could pass through an otherwise clean surface (e.g. a piece of glass). Something “opaque” completely prevents light from passing through; therefore, the word “translucent” is the best option among those provided, as it means allowing light to pass through. The “trans-” prefix, meaning across, is added to “-lucent,” which means pertaining to light. It therefore literally means letting light across.

This whole set of words is related to being clean, however, not to the same degree. To be “sterile” is to be completely free of any dirt or potentially infectious material. Even something “sanitary” (clean and generally safe with regard to health) is not necessarily as clean as something that is completely sterile; therefore, “sterile” is the word least related to the others.

"Philanthropic" means charitable. If a person is "haughty," "conceited," "pompous," or "pretentious," she is arrogant, or thinks her abilities are superior to everyone else's. All four of these words describe more than just confidence. Also, all four of these terms are pejorative, and philanthropic has positive connotations.

"Devoid" is an adjective meaning entirely lacking. I might say, "The terrorist was devoid of all emotion." "Brilliant," "clever," "canny," and "astute" are all synonyms for the word "intelligent."

"Mutinous" means to refuse the orders of a superior. It is usually applied to people in the armed forces. "Disgusting," "revolting," "abhorrent," and "vile" all imply something that creates a feeling of strong disgust. For example: "Cleaning the outhouse was completely vile." You could substitute any of the other three words for "vile" and have the same basic meaning.

Although all of these words mean "silent," four of them are adverbs and one is an adjective. Adverbs describe how a verb is performed. For instance, HOW does Johnny run?  He runs quickly. Quickly is the adverb. Most adverbs end in -ly. "Inaudible" is an adjective. Adjectives describe nouns. For instance, "The actor was inaudible over the noise of the crowd." Inaudible is the adjective describing the actor, a noun. 

All five words can be used to describe a person. "Beautiful," however, is generally used to describe a person's physical appearance. "Deranged," "curious," "brilliant," and "methodical" are generally used to describe a person's personality or state of mind.