问答题
But barriers are easier to [填空1] than to remove, so the share of trade held back by protectionist measures tends to grow over time.
【参考答案】
1、put in place
点击查看答案
．从t = 0时刻起，到质点位置在x = -2 cm处，且向x轴正方向运动的最短时间间隔为 （）
