Answered

why did Roosevelt feel the need to propose expanding the number of justices on the Supreme Court?

AThe Supreme Court have been striking down in New Deal programs as unconstitutional
Bthe Supreme Court have been struggling under a heavy workload
Cthe Supreme Court didn't consider his election valid
Dthe Supreme Court was refusing to hear new cases.

Verified Answer :

The answer is letter A.
Before Roosevelt introduced this plan, the Supreme Court have rejected
many elements of his New Deal plan because the authority held by the Executive
was too much and considered unconstitutional.
He thought that by adding more justices to the Supreme Court, it would
protect his legislation.  Still it was
rejected by both liberals and conservatives.