登楼梯比赛时,某同学从底楼匀速登上五楼,共用了12 s,该同学登楼时克服重力做功的功率最接近于 [ ]
A.500 W
B.100 W
C.50 W
D.10 W
答案:A
If you love someone, why ______ you chain him to your side, control his emotion, and even make him center on you?
A.must
B.dare
C.need
D.will
关于布氏杆菌病原学的特征,不正确的是()
A.革兰染色阴性
B.是多形球杆菌
C.无鞭毛与芽胞
D.可形成荚膜
E.细菌释放的外毒素为主要致病因素