公债的基本特征是()
A.自愿性
B.固定性
C.有偿性
D.灵活性
E.强制性
参考答案:A, C, D
______ that the formation of the sun, the planets, and other stars began with the condensation of an interstellar gas cloud.
A.It is believed
B.To believe
C.To be believed
D.Believed
左旋多巴的不良反应有()
A.嗜睡
B.齿龈增生
C.精神障碍
D.运动障碍
E.开-关现象