在北京城市建设中,对待历史悠久的胡同,正确的做法是( )
A:全部拆除
B:原封不动保留
C:根据建设需要拆除
D:有选择地保护和改造
As more and more cars are produced and used, the emission from their exhaust pipes contains an even larger volume of ____ (poison) gas.
— Jane, can you play ________ baseball?
— No, I can't. But I can play ________ violin.