Which correction should be made to sentence 7?

— ExhibitC

Sentence 7:Thus, to ensure that everyone is given an equal opportunity for a quiet working area, you are requested to observe this new policy.

Which correction should be made to sentence 7?
A . remove the comma after Thus
B . insert a comma after ensure
C . remove the comma after area
D . change are to is
E . no correction is necessary

Answer: E