The school bus was ______ by a thick fog.
32. Fireworks, ________ of gun powder or flash powder _______ in a tight paper tube, make the big flash or boom effect.
31. In the past few years, research has suggested that Vitamin D may increase the level of serotonin(血清素), one of the key neurotransmitters influencing our mood, and ________it helps to relieve mood disorders.
30. Chinese must have the largest number of speakers, ________ ?
28. More Than a Game, a documentary which follows NBA star LeBrown James’s path _________ a star, came out on October 2, 2009 in the US.
27. A: What’s the matter, Sara? You wear a sad look on your face. B: Oh, nothing much. As a matter of fact, I _______ of my friends back home.