by后面加什么 cover

1、He had attempted to cover his tracks by making her death appear like suicide.他使她的死亡看起来像是自杀，企图以此掩盖自己的罪行。

2、The insurance policy does not cover damage caused by normal wear and tear.保险单内容不包括正常使用所导致的损坏。

3、Design of breaking ice cover by pressure flow in sedimentation Basin by.水厂平流沉淀池压力水流破冰方案设计。