must be sb doing 某人必须做.
see sb do是全过程,doing是看见某人正在做
watch sb 同上
hope to do sth,不能用hope sb to do sth句型 可以是hope +that 同位语从句.
如 His hope that he will have a large house one day is not impossible.
expect sb to do sth,希望某人可以做某事