Scientists photographed for the first ti
问题:
Scientists photographed for the first time ever _____ wild gorillas used a stick to test the depth of a pool before getting into it, according to a recent study.
A.which
B.what
C.that
D.when
Scientists photographed for the first time ever _____ wild gorillas used a stick to test the depth of a pool before getting into it, according to a recent study.
A.which
B.what
C.that
D.when