D) has saved
Perfect present tense indicates that something happened at some point in the past or began in the past and is continuing into the present time. The woman saved $60 in the past and is still saving $60 now by taking the bus. The perfect present tense is created using the /to have/ form + past tense form of the main verb. "Saves" is written in present tense. "was saving" and "saved" are both past tense forms.
