Drivers should drive the car【as carefully as possible 】 (尽可能小心)还有同义句捏好吧，同义句应该是：Drivers should drive the car as carefully as they can. as ……as possible =as ……as one canDrivers --- --- ---drive the car --- 有四个空啦······你确定题目没给错？我觉得可以这样填：should do their best to ，carefullydo one's best to do sth 尽力做某事这两句都必须用carefully ，不能用 careful 。