问题补充：
Tough the task was, we finish it ahead of time and therefore we were highly praised for it.
A. though; would
B. although; had to
C. as; were able to
D. though; must
答案：
A. though; would
B. although; had to
(答案→)C. as; were able to
D. though; must
解析：考查as的倒装句以及固定用法。Be able to do sth指经过努力能够做某事；have to指客观上不得不做某事；本题重在掌握as“尽管”时可引起倒装，同时although引导让步状语从句时不能倒装，as引导让步状语从句时必须倒装，而though引导让步状语从句时可以倒装也可以不倒装。句意：尽管这个任务很难，我们还是能够提前完成的，因此我们会因此得到高度赞扬。故C正确。
