Which of the following sentences contains at least one error?

a$.$ Chris is very motivated to succeed and determined to conquer any challenges placed in front of her.

b$.$ Whether or not the proposal is a popular one, we still must make an effort to comply with the provisions

c$.$ Although the previous employee's in the program were very qualified, this new group seems exceptionally capable.

d$.$ The ability to set priorities and manage time is essential to being an effective employee.

e$.$ None of the above sentences contain errors.