（2017·四川德阳·33）My mother has taught in this school________ she was twenty years old.
A.for B.until C.because D.since
-What is your mother doing, Linda?
-She ___________dinner in the kitchen now.
A.is cooking B.was cooking C.cook D.cooking
Dingtalk is a tool _______ is mainly used for teachers and students to have online classes during the fight against the novel coronavirus.
A.which B.who C.where D./
He isn't at school. I think he ___ be ill.
A.can B.shall C.must D.has to
— is it from your school to the bus stop?
— It’s about 5 minutes’ walk.
A. How often B. How long C. How soon D. How far
My father is very busy．He has spare time．
A. always B. usually C. seldom D. sometimes
