A：自行车轮胎上制有凹凸的花纹
B：用橡胶制作自行车的闸皮
C：自行车轴承中装有滚珠
D：骑自行车的人刹车时用力捏闸
She found ____ difficult to settle and calm down in the ____ place, because she was worried about whether they would be discovered.
鉴真东渡、玄奘西行、郑和下西洋反映的共同的主题是（ ）
世界因生命而美丽，让我们珍爱生命。
请回答：
