Since Marshall was having a hard time understanding calculus. He begged Lily to tutor him after school in the library.
What is the best way to join the clauses into one complex sentence?
A. Since Marshall was having a hard time understanding calculus he begged Lily to tutor him after school in the library.
B. Since Marshall was having a hard time understanding calculus; he begged Lily to tutor him after school in the library.
C.
Since Marshall was having a hard time understanding calculus, he begged Lily to tutor him after school in the library.
D.
Since Marshall was having a hard time understanding calculus, and he begged Lily to tutor him after school in the library.