Choose the sentence with correct comma usage.

A- Since Professor Beck was on sabbatical Franklin asked Ms. Yamada to critique his
novel and she agreed to offer her guidance.

B- Since, Professor Beck was on sabbatical Franklin asked Ms. Yamada to critique
his novel and she agreed to offer her guidance.

C- Since Professor Beck was on sabbatical Franklin asked Ms. Yamada to critique his
novel, and she agreed to offer her guidance.

D- Since Professor Beck was on sabbatical, Franklin asked Ms. Yamada to critique
his novel, and she agreed to offer her guidance.