The key thing to note here are the number of terms involved. A “couplet” (like a “couple”) has only two members in it.  If something is “ternary,” it has three parts, like the “triad” (three part structure): “being, life, and intellect.”

The key word here is “health,” which is best matched by “insalubrious,” which means unhealthful. Something that is “salubrious” is healthful. The word is related to the simpler Latin root “salus,” meaning health, prosperity, or [even] greeting. It is related to English words like “salvation” and “salutation.” 

Although you might be tempted to choose “health,” we can surmise more accurately that the old man had kidney problems—hence the need for a kidney transplant, though certainly this is itself a type of health issue. The adjective “renal” means pertaining to the kidneys. It is found in the word “adrenaline,” now called “epinephrine,” because the “adrenal” glands are on the kidneys: ad + renal.

The thing to be noted here is the contrast between the outer muscle and the inner muscle.  Now, a number of the words are meant to tempt you into this simple form of reasoning, but you must always choose the best word. Since we are considering a heart attack specifically, the kind of muscle involved (in the heart) is “cardiac.” When someone has a “cardiac arrest,” that person’s heart has stopped its regular beating and no longer effectively delivers blood.

Since the argument was haphazard, the conclusions would seem very unlikely in their final claims. To be “dubitable” is to be “doubtful.” It comes from the Latin word for “doubt.” The latter (“doubt”) is close to “dubitable” in English form, but other related words are “indubitably” and “dubious.”

Although a number of the options given for this question are tempting, the key point is that John does not want to be in others’ sight. Do not be tricked by the expression “far removed” as though it necessarily implies distance. It merely indicates that he wishes to be out of vision of the general crowd. The word “inconspicuous” means not in general visibility. If something is “conspicuous,” it is readily seen and obvious. The “-spic-” root is likewise found in other “-spec-” words that are legion in the English language, coming from the Latin roots for to look. Such words include (among many others): “spectator,” “prospective,” “perspective,” “specific,” “spectacular,” and so forth.

The key words in the second sentence are “indivisible” and “atomic.” Although “corpuscle” often is used to describe the smallest part of a given biological body, it also can be used to mean the smallest indivisible unit. When science began to focus on the atomic structure of matter—which never was really forgotten, though it was not given a lot of prominence for other reasons—there was much talk of the “corpuscular,” that is, atomic nature of the world.

The key word that indicates what is needed is “introduction.” This is best matched by the word “propaedeutic”—a rare word, but one that can be discerned. The prefix “pro-” is the same as that found in the word “prologue,” meaning “coming before.” The root of “-“-paedeutic” is a bit more difficult, but it is related to such “teaching-related” words as “pedagogue” and “pedantic.” A propaedeutic subject is one that is introductory, leading onward later to further instruction after setting the initial groundwork.

The opposition with “lax and disorganized” implies that the person is very aware and careful about details in at least one area of life. To be “fastidious” is to have such particular care about details.

The focus in this sentence is on the engineers’ ability to use the water. While perhaps their design is amazing, the word “hydrodynamics” means “concerned with the forces of water.” You know the parts to this word “hydro-” being found in other water-related words like “hydrate,” “hydroelectric,” and “hydrolysis.” The portion “dynamics” is found in a number of “dynamic” words including “aerodynamics,” “dynamism,” and “dynamite.”