Which enzyme catalyzes the elongation of the leading strand?

A. RNA polymerase
B. Helicase
C. DNA polymerase
D. Ligase

C

There were many complaints about this question, and as a matter of fact it turned out to be the second question in difficulty and not that good at discriminating between good and weak candidates. Many candidates believed helicase is in charge of elongation of DNA, the syllabus clearly states that helicase only unwinds DNA for DNA polymerase to act.  It was agreed that this question was more appropriate for HL than for SL, but it could still be answered with the knowledge acquired in SL.