现有5名教师要带3个兴趣小组外出学习考察,要求每个兴趣小组的带队教师至多2人,但其中甲教师和乙教师均不能单独带队,则不同的带队方案有____ 种.(用数字作答)
Only good swimmers can get to that place. There is water all ________ it.
下列措施中,能增大摩擦的是( )