He doesn’t know ________ they will plant trees on Saturday or not.
The 30th Olympic Games ______ in London this summer.
I ______ much progress in my English study since last term.
They will call us as soon as they ______ there.
— Were you at home at that time? — No, I ______ dinner with my friends in a restaurant.
— Which do you think is ______ subject, math, music or art? — Art, I guess.