The twins didn't go to the theatre, they ____ the light music all night.
A:have enjoyed
B:will enjoy
C:are enjoying
D:were enjoying
M、N都是质数,M+N的和小于50,且是7的倍数,如果M+N又是奇数,那么N×M 可能是( )
人在恐惧、紧张时,在内脏神经的支配下,肾上腺髓质释放的肾上腺素增多,该激素可用于心脏,使心率加快.下列叙述错误的是( )