When the head teacher was walking past the window, she noticed two students _______ chess in class. She really got _______.
A:playing; annoyed
B:playing; annoying
C:play; annoyed
D:played; annoyed
在化学反应前后一定发生变化的是( )
如图所示,实验室里有一套用来制取气体的装置,下列有关叙述正确的是( )