There _____ a lot of coal mines in the south, but many of them have been closed or are _____ be closed.

On May 5, 2018, various memorial events were held nationwide ________ the 200th Anniversary of Karl Marx’s birth.

— I have come to say good-by.— What time_____?[ ]

I have a lot of homework to do today,_________ I cannot go swimming with you.

President Xi Jinping demanded the environmental problems _______paid special attention to.