Official Explanation
For a quick, general sense of the opening clause, break it down. What does it say? Critics ______ the movie’s sugary sweet tone.
How would critics react to something sugary sweet and overly hopeful? Most likely they would not acclaim (praise) it. You are probably safe to cross out the word acclaimed. However, they might well decry or disparage it. They might even echo or copy it, although that answer choice seems unlikely.
You have two possibilities for the first blank, decried and echoed, with the former more likely than the latter. Now consider the second blank. The movie’s sugary, overly hopeful tone is out of keeping with the novel’s quality: the two tones disagree. Therefore, the novel’s tone is not sanguine (hopeful) or cloying (sickly sweet). It is instead on the bitter or sour side; in a word, acerbic.
Answer: B,D