动机是激发和维持有机体的行动，并使该行动朝向一定目标的心理倾向或内部驱力。（ ）
参考答案：对
引起人类性传播疾病的病毒是（）
A.人巨细胞病毒
B.EB病毒
C.轮子状病毒
D.单纯性疱疹病毒
E.人 * * 瘤病毒
—I rang you at about nine, but there was no reply.
—Oh, that was probably__________I was seeing the doctor.
A．why
B．when
C．what
D．that
