I think this test is ... than the one we did last month. A. as difficult          B. difficult          C. the most difficult          D. more difficult

I think this test is as difficult as the one we did last month.

I think this test is more difficult than the one we did last month.

I think this test is the most difficult than the one we did last month.

I think this test is difficult than the one we did last month.

I think this test is as difficult than the one we did last month.