In addition to the boom in tax revenue, the federal

Option A:- correct
Option A are being helped by lower defense spending, a drop of in outlay for benefits like Medicaid, and proceeds from the sale of General Motors and Chrysler, the automakers. This option maintains proper parallelism by using the preposition for the first item and going over it for the rest.

Option B:- Incorrect
Have been helped by lower defense spending, a drop in outlays for benefits like Medicaid, and by proceeds from the sale of General Motors and Chrysler, automakers. Present perfect tense is used instead of simple present tense. 'by proceeds' break the rule of parallelism. Also Article 'THE' is removed.

Option C:- Incorrect
Have been helped by lower defense spending, a drop in outlays for benefits like Medicaid, proceeds from the sales of General Motors and Chrysler, and by the automakers.
The conjunction 'and' is removed thereby distorting the structure of the sentence present perfect tense, error repeats here and by the automakers incorrectly modifies General Motors and Chrysler.

Option D:- Incorrect
Are being helped by lower defense spending, by a drop in outlays for benefits like Medicaid, and proceeds from the sale of General Motors and Chrysler, the automakers. By a drop is not necessary modifier makes the sentence invalid.

Option E:- Incorrect
Were helped by lower defense spending and a drop of the outlays for benefits like the Medicaid, Also by proceeds from the sales of General Motors and Chrysler, the automakers. The past tense 'were helped' is used here instead of present tense. The unimportant modifier is made parallel to the main sentence also 'by proceed' does not make any sense by meaning.