Question

Believe it or not, _____ did I hear it, but also saw it.

A. as well
B. not only
C. never before
D. only if

Answer 1

答案B
考察倒装句。Not only…but also…不但…而且…;not only放在句首，要部分倒装。AD两项放在句首，不要倒装。C项与现在完成时连用，表示倒装。故B正确。