However much scientists may agree that the average global temperature

However much scientists may agree that the average global temperature is rising and that this rise is at least partially caused by human activity, global warming remains a subject of heated debate for both American citizens and lawmakers.


(A) However much scientists may agree that

'However' is being used in the sense of 'to whatever extent' and should not be confused with the use of 'however' to suggest contradiction. The 'may' suggests that scientists do not definitely agree. As such there is nothing wrong grammatically wrong with this answer choice. Many of the following answer choices will grammatically sound too; however, they will change the meaning of this sentence, thus making them invalid.

(B) Despite agreement among scientists to the fact

'to the fact' is wordy.

(C) Although scientists agree

Changes original meaning of sentence from 'may agree' to 'agree.'

(D) Even though most scientists may agree

Here the extent of the agreement is not being addressed the way it is in the original sentence.

(E) There is agreement among many scientists that

This answer choice is even more stark then (D). Suddenly many scientists are agreeing, an occurrence that would change the meaning of the original sentence.

Hope that helps