With a lot of difficult problems________, the manager felt worried all the time.[ ]

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

单项填空One of the best ways for people to keep fit is to ________healthy eating habits.[ ]

Mike _________ English, but now he is better at itthan _________ in his class.

________ with the size of the whole earth, the biggestocean does not seem big at all.