A:①②③④
B:①②③
C:②③④
D:①②④
①把装置连接好
②两手紧贴容器外壁使容器内的空气受热膨胀
③观察导管口有无气泡冒出
④把导管的一端浸入水中.
—What does your Chinese teacher look like?
—She of medium height.And she short hair.