1. We must reinforce the troops at the front.
    我们必须加强前线部队的力量。

2. While explaining something to others, students reinforce their own knowledge about the subject.
    学生在给其他人解释问题时，自己对该问题的认识也加深了。

3. They should regularly check and reinforce their homes, place heavy objects in low positions, attach cupboards and cabinets to walls, and fasten doors so that they will not open accidentally during an earthquake.
    他们应当定期检查和加固房屋，将重物放在低处，将碗橱和柜子贴墙放置，加固房门以防地震时突然脱开。