Mum won’ t let Simon go out unless he promises to be back ______10 o’ clock tonight.
A. till B. before C. as D. since
(2019原创)The best way of solving the problem is to keep ________ trying.
(2019原创)It's very kind________ you to help me with my lessons, because it's hard for me to learn them well.
(2019原创)We can listen ________ some soft music to make us feel relaxed.
(2019原创)Sarah is very good________ dancing and singing. She wants to be an actor in the future.
(2018唐山开平区二模)After hearing f________ her sister, she read the letter and wrote back in no time.
