【正确答案】 B

【答案解析】be supposed to do sth．“理所当然要去做某事”：He is supposed to arrive on the five o'clock train. be known to do sth．据知…在做…，没有句型sb．is regarded to do sth．，也不能说sb．is considered to do sth．。句意：他在看电视?他应该在打扫他的房间。