Look at my watch. It's 8 _______.
A:o'clock
B:clock
C:clocks
分数 的分子和分母的最大公因数是____,化成最简分数是____。
First-class players of football must have excellent ball control, but it is not just _____ they do with their feet _____ counts.
下表是某实验小组同学做“研究滑动摩擦力的大小跟哪些因素有关”的实验记录: