有X、Y、Z三种金属,如果把X和Y分别放入稀硫酸中,X溶解并产生氢气,而Y不反应;如果把Y和Z分别放入硝酸银溶液中,过一会儿,在Y表面有银析出,而Z没有变化.根据以上实验事实,判断X、Y和Z的金属活动性顺序由弱到强是( )
A:X<Y<Z
B:X<Z<Y
C:Z<Y<X
D:Z<X<Y
643的平方根为____
转动粗准焦螺旋使镜筒下降时,眼睛应注视( )
I ____ (not listen) to the radio now.
him sleep quick hurt smell
①Do you know why Jenny ran ____ out of the room?
②The baby is too young to look after____.
③I got up too early and I'm feeling very ____ now.
④My brother ____ his leg when he fell off the bike.
⑤This flower sends out one kind sweet ____.