单项选择题
（）learning has a lot to do with your hard work.
A.successfulB.succeedC.successD.succe
单项选择题 线粒体DNA遗传的特点是（）。
单项选择题 （）the grand city was a small village ten years ago.
单项选择题 He has to go to Canada for the next（）of his training.
