火花型海发光的主要发光生物类型为()。2015年山东东营海边出现的蓝色“荧光海”,可能就是该类型发光生物所致。
A、发光鱼类
B、水母
C、发光细菌
D、小型浮游生物
参考答案:D
Under these_________, you might agree with us that it is rather difficult for our products to put a
footing on this market. [ ]
A. situations
B. cases
C. circumstances
D. conditions
在圆柱齿轮传动中,常使小齿轮齿宽b1略大于大齿轮齿宽b2,其目的是()