Your question asks which sentence is grammatically correct.
The reason why answer choice "A). claims suggest that the economy might not be as weak as some analysts previously thought" is correct because the plural verb matches with the plural subject in the sentence. The word "suggest" is used right and the phrase "as weak as" is correct too.
Plural subject: Surge and drop
Plural verb: Suggest
(B) claims suggests that the economy might not be so weak as some analysts have previously thought -- the word "suggests" is singular, so it won't match the plural subject in the sentence.
(C) claims suggest that the economy might not be as weak as have been previously thought by some analysts -- The "have been previously thought" in the sentence doesn't sound right, it sounds weird. Therefore, it makes this sentence incorrect.
(D) claims, suggesting about the economy that it might not be so weak as previously thought by some analysts -- This sentence makes in sound like the plural subjects are suggesting something, in which they aren't, the analyst are the one's that are suggesting. This sentence is also very wordy. Therefore, this is incorrect.
(E) claims, suggesting the economy might not be as weak as previously thought to be by some analysts -- This sentence is also a bit wordy. It also makes it seem like the plural nouns are suggesting about the economy, but they aren't, the analyst are the ones that are suggesting. This is just like answer choice "D." This answer would be incorrect.
