英语题目16．Could you tell us ______ Mr Brown lives in Room 202?

英语题目
16．Could you tell us ______ Mr Brown lives in Room 202?
A．that B．where C．un til D．if
17．Do you know ______ he did not turn off the light?
A．how B．why C．what D．whether
18．I don't know ______ or not it will rain tomorrow．
A．that B．when C．if D．whether
19．—Why is their classroom so clean and tidy?
— ______ it is cleaned every day．
A．Since B．As C．Because D．For
20．Can you tell me ______ is going to give us a talk next Monday?
A．who B．whom C．whose D．what