What is the shape of buttress thread flank?

A. One flank is 90 Degree and the other 45 Degree

B. One flank is 30 Degree and the other 45 Degree

C. One flank is 60 Degree and the other 45 Degree

D. Two flanks are at 60 Degree

Correct Answer: One flank is 90 Degree and the other 45 Degree