---- ________ class are you having? ---- Math.
For the safety, everyone _________ obey the traffic rules when he is driving or walking.
This summer vocation I am going to do a lot of _________ to prepare for the senior high school.
--Did you see Mary and her sister this morning?-- Yes, I saw _________ girls playing in the playground.
Although advertisements enable _________ to make decisions quickly, they sometimes cause lots of trouble.
Over 20 countries joined to search _________ Flight MH370 in the southern Indian Ocean.