单选题 Since 1990, our customers ______with our service.

A、 (A) are satisfied
B、 (B) have satisfied
C、 (C) have been satisfying
D、 (D) have been satisfied

【正确答案】 D

【答案解析】Have been satisfied is the passive form of the present perfect tense, which indicates an action that started in the past and continues to the present. Choice (A) is the present tense. Choice (B) is the present perfect (active form). Choice (C) is the present perfect continuous.