At first glance, the two blanks seem to be opposites, but pay attention to the words "far less" before the second blank. We're actually looking for two synonyms, something that would "feel insurmountable" - "overwhelming" or onerous (burdensome). 

We are looking for two opposite words. Only "pernicious" (meaning extremely harmful) and "innocuous" (meaning harmless) work.

“Ambiguous” means uncertain or open to interpretation. It would be hard to argue that the effects were “ambiguous” when “every yard in the neighborhood had parched grass.” “Ample” means having more of something than is needed, often much more. When something is “conspicuous,” you notice it right away. “Conspicuous . . . ample” is the correct answer.

An “amulet” is an object that is believed to protect against harm or bring good luck. “Serendipitous” conveys a two-part meaning: lucky and unexpected. “Uncanny” refers to something being so strange and abnormal that it seems supernatural, which fits well in the sentence. “Uncanny . . . serendipitous” is the best answer.

We know from the last part of the sentence that the stranger was accused of theft; therefore his intentions must have been bad (nefarious), and that he was casting secretive looks (furtive). 

Our first clue is that "even a short walk was tiring" for Keisha; therefore, she must have been weak ("enervated"). The word "nevertheless" indicates a shift in direction; despite her weakness she wants to go out, believing it will be healthy ("salubrious") for her.

The word "although" tells us that the sentence will shift meaning. The fact that the jury "failed to convict him" despite the strong evidence, suggests he was actually guilty ("culpable"); however, we was able to charm the jury, with his friendly ("affable") nature. 

The wife could "prattle for hours" - she was very talkative ("garrulous"); her husband was the opposite, a "man of few words" ("laconic"). 

The clue for the first blank is that Troy "rarely spoke up" - he was reserved/shy ("diffident"). The second blank is contrasted with the impression that he was "lacking in intellect," but he was quite intelligent or well-learned ("erudite").

As with any two-or-three-blank text completion question, you should start by identifying which blank is the most limited in its potential answers. In the context of the sentence, the first blank seems to allow for countless possibilities. As it turns out, a quick glance at the answer choices reveals three answers which seemingly might satisfy this first blank. So instead, we will start with the second blank. As indicated by the "effluence of rotting food," we are in search of a word which means bad-smelling. Of the answer choices, only "noisome" matches this description. To confirm our answer, we see that "squalid" fits properly in the first blank, and thus we have arrived at the correct choice.