“观察小鱼尾鳍内血液的流动”实验中,寻找毛细血管的最好方法是[ ]
A.血液流向头部的血管
B.红细胞单行通过的血管
C.血液流向尾部的血管
D.血流速度较快的血管
B
How _______ the song she sings sounds! I have never_______ a better voice.
A.beautifully; sounded
B.beautiful; heard
C.sweet; listened to
D.sweet; sounded
就人体触电而言,交流相比直流( )。
A.更易于摆脱 B.更难于摆脱C.对人体伤害二者相同 D.交流有效值与直流对人伤害效果相同