短语讲解：

1. Police in northern Afghanistan said Tuesday unknown gunmen have shot dead at least nine employees of an aid agency.

at least 至少
例句：In fact it requires at least n generators.
事实上，它至少要有n个元素。

2. American telephone companies will take over the task in six months.

take over 接管; 带; 帮…学习; 在…上花费
例句：Have a rest. I'll take over.
你歇会儿, 我来替你。