A:an apple
B:apples
—It is very _______ for kids to stay in a small room for too long.
— is your favorite teacher?
— Paul. I like his class.
A
B
C
D
锥形瓶
MnO2
Zn
H2O
HCl气体
胶头滴管
H2O2
稀H2SO4
浓H2SO4
石灰水