——It won't take long to clean our school if all the students are willing to help. ——Yes, I think so. ________.
A:Too many cooks spoil the broth
B:Don't put all your eggs in one basket
C:Many hands make light work
D:Every dog has its day
根据汉语把英语句子补充完整。
如图所示的杠杆是____杠杆(选填“省力”或“费力”)。图中O为支点,F1的力臂为l1,F2的力臂为l2,当杠杆平衡时,F1与F2定量的关系式为____。