—When will your father come back? —I don’t know. I will tell you _____ he comes back. A. before B. as soon as C. until D. and 答案:B18.如图是实验室制取气体的部分装置.(1)写出一个用A装置制取O2的化学方程式2KClO3$\frac{\underline{\;MnO_{2}\;}}{△}$2KCl+3O2↑.(2)B和C装置均可制取CO2,其中C装置与B装置相比优点是什么?可随时控制反应的发生与停止.(3)若用D装置收集H2,则H2应从b端通入(填“a”或“b”)