D) arrived yesterday in the mail
The predicate is the part of the sentence that contains the verb (action word). The verb in the sentence is arrived. This eliminates options A and B, as these options do not contain the verb. When finding a verb it is helpful first to find the subject (Who or what is the sentence about?). After you find the subject, you ask yourself is the subject being described or is the subject doing something? In this sentence the subject grades did something - grades arrived. The predicate starts with the verb phrase so this means the correct answer is D.
