D, the best answer, is the first one that I excluded ;)
OG104 kEY: (D.)
Spending on R&D by US businesses for 1984 showed an increase of about 8 percent over 1983 level. This increase actually continued a downward trend evident since 1981-when outlays for R&D increased 16.4 percent over 1980 spending. Clearly, the 25 percent tax credit enacted by Congress in 1981, which was intended to promote spending on R&D, did little or nothing to stimulate such spending.
The conclusion of the argument above cannot be true unless which of the following is true?
D. In the absense of the 25 percent tax credit, business spending for R&D after 1981 would not have been substantially lower than it was.
E. Tax credits marked for specific investments are rarely effective in including businesses to make those investments.