问题补充：
He was unable to make such progress, .
A. as he tried hard
B. as hard he tried
C. so hard did he try
D. hard as he tried
答案：
A. as he tried hard
B. as hard he tried
C. so hard did he try
(答案→)D. hard as he tried
解析：本题是由as引导的让步状语从句，将表语或状语提前，结构是“表语/状语+as+主语+谓语”。
