be covered with 被…所覆盖,覆盖着,盖满…
The grass was covered with frost in the early morning.
The tree was covered with beautiful pink blossom.
be covered by ...:由...承担/负担/支付;被...掩护/报道/监视/控制等等,表示抽象的概念,后面接人,机构,或者组织.
These expenses are covered by the state.