trade for:
以...换得
The boy traded his knife for a football.
男孩用小刀换得一个足球。
What will you trade for the bugle?
你要我用什么东西来换你的喇叭?
exchange for:
1.交换,调换,兑换
They sold eggs in exchange for salt and tea.
他们把鸡蛋卖掉换取茶叶和盐。
The kid napers demanded money in exchange for her safe return.
绑匪们要求以金钱换取她的平安交还。
sign on
1.签约受雇
He signed on as a sailor.
他签约受雇为船员。
sign-on
名词 n.
1.【广播】开播