—He asked me _____ .
A：whom I was chatting with
B：where I am with my friends
C：when would I go home
D：if I have finished my homework
实验室收集氧气时，可采用向上排空气法，原因是通常情况下：____ ；也可采用排水集气法，原因是通常情况下：____ ．有一集气瓶，要想测量该集气瓶最多能收集气体的体积，请你写出简便的测量方法（可以选择必要的器材）：____ ．
(203÷7＋21)÷5=30
