The best way to work through a complex text completion such as this is to try and determine what each blank is referring to and what is known about that subject matter as you read the sentences from beginning to end. On the actual exam it can be beneficial to literally write out the initials RT and K to indicate refers to and know, so we will do that here as well. Let's begin with the first of the blanks.

The introductory sentence seems superfluous to begin and does not reveal much about the first blank at the beginning of the second sentence. So what do we know as we encounter this first blank? So far, nothing. But immediately following blank 1, it is determined that "disease rates fell", so we can write out RT: what there was | K: disease rates fell. Now, move to the choices looking for something that would match this positive outcome of disease rates falling. Let's be honest, choice A: lagniappe is probably not a familiar word to most English speakers, so this should probably be annotated by a ? indicating that the definition is unknown and therefore the choice cannot be eliminated. Next, choice B: avarice, this too could be a ?, but maybe, you recognize the root of "ric" indicating riches, which would not be relevant for the prediction, so eliminate choice B. Then, perhaps for choice C:recidivism, you know that it means to commit an offense for a subsequent time. This means, that whatever lagniappe is, it's the best option. Now, continue onto the second blank, but knowing that the first blank is a best guess, move to evaluate the rest of the sentence by briskly predicting for tone only because that unknown term of lagniappe may or may not be correct.

The second blank clearly refers to "floodwater" where mosquitos could breed, so for blank 2 simply predict this as negative in tone and look to the choices for something that could describe water negatively. Choice D: fascistic is negative and can probably be identified as such because of the root "fascist", but water could not be described as fascist, so eliminate D. Next, choice E: fetid is negative and could describe water, so proactively select it with a ✓. Then, always check the final choice F: macabre is negative, but water cannot be described as such, so select choice E before moving to the final blank.

Then, the final blank rather clearly refers to the word breed, which in classical terms would be positive in tone. Choice G: obviate and in fact opposite in tone to the sought predicted positive tone. Choice H: profilate is another very obscure term, but the root of "pro" could possibly be identified as positive in tone, so keep choice H with a ~. Then, check the last choice I: dwindle, which is another reversal in tone. So, even without knowing all of the terms in the choices, you can work through the options considering only tone to arrive at the correct options of A, E, and H!

P.S. lagniappe means "an unexpected benefit"