On hearing of the case some time later, Conan Doyle was convinced that the man was not guilty, and immediately went to work to ascertain the truth.

A. explore
B. obtain

C. verify

D. search

我们应当把对外开放的根本立足点放在（）

A.发展对外经济关系上

B.发展睦邻友好关系上

C.增强我国独立自主、自力更生的能力上

D.吸引和借鉴世界一切文明成果