We should do everything we can _______ the birds _______ danger.

A．to protect; away

B．to protect; in

C．protecting; in

D．protected; from

白醋（含3%-5%的醋酸）是常用的调味品。现有4%的白醋500g，该溶液中含溶质醋酸      g；若再加水500g稀释后所得溶液溶质醋酸的质量分数为      。