so you are saying it should be catalyst?
right?

Carcass I believe the answer key should say Catalyst instead of Antidote. Please correct me if I'm wrong.

Yes correct sir. My bad

I fixed the typo for the first blank which was indeed A and not C as reported

OE


The first sentence informs us that the death of Hu Yaobang caused the protests, so we are looking for a word that describes something that causes something else. An antidote (something that prevents or counteracts injurious or unwanted effects) causes improvement, but that clearly will not work in this sentence, which describes events culminating in a massacre. Imbroglio will also not work; it means a misunderstanding or an intricate and perplexing affair, and better describes the circumstances following Hu Yaobang's death than the death itself. The correct answer is catalyst, which means a thing that precipitates an event or change.
As for the final two blanks, you should be able to glean from the rest of the passage that the government responded to the protests in a particularly savage way that was probably not received well in other countries, so you should be looking for words in keeping with this. Redoubtable means formidable, and it often implies respect, which is clearly not appropriate here - eliminate it. Dubious means questionable and is also not a good choice; there is no question that the government's actions were unethical. You are left with heinous (hateful or totally reprehensible).
As for the last blank, encomium would certainly not be an appropriate response; it means a formal expression of high praise. Sanctimony is also a bad fit; it means pretended, affected, or hypocritical religious devotion, righteousness, etc. Opprobrium (reproach or censure) seems a quite likely reaction, however, and is the correct answer.