Question

David doesn’t give up _______ he has failed in the experiment four times.

A．if

B．while

C．though

D．since

Answer 1

C

连词辨析。if 是否，如果；while当……时，然而；though虽然，尽管；since自从……以来，由于。句意：尽管他在实验中已经失败了四次，但是戴维德还不放弃。故选C。