一种新病毒株攻击呼吸系统。

A new strain of virus ___attacks the respiratory system.

许多感染攻击免疫力弱的儿童。

Many infections ___attack children with weak immunity.

刺激性化学物质可能攻击皮肤，引起刺激。

Harsh chemicals can ___attack the skin, causing irritation.