It is helpful
if a banker who frequently analyzes companies has a strong background in math and accounting, as well as a good dose of common business sense.
A. if a banker who frequently analyzes companies has a strong background in math and accounting
B. if a banker who frequently analyzes companies uses
their strong background in math and accounting
"A Banker" should be paired with "his" and not "their"
C. if a banker who frequently analyzes companies
have a strong background in math and accounting
"A Banker" should be paired with "has" and not "have"
D. if a banker who frequently analyzes companies,
which requires a strong background in math and accounting
"Which" is referring to "companies" but ideally it should be referring to the "Banker"
E. if a banker who frequently analyzes companies
require a strong background in math and accounting
"Require" should be "Requires" since "Banker" is singuler
There is Subject-Verb mismatch in Options B, C, and E. In D "WHICH" has a wrong referent.