A:N
B:M
C:L
D:K
已知圆环的外圆半径为46mm,内圆半径为27mm,求圆环的面积(利用计算器计算,结果精确到十位).
I
Take a shower
My mother
Clean the kitchen
My father
Watch TV
My elder sister Alice
Work on the computer
下列操作中,能鉴别空气、氧气和氢气3瓶气体的是