重点讲解：
1. in contact with 接触；遇见；
Have the children been in contact with the disease?
孩子们同这种疾病有过接触吗？
2. search for 搜寻；搜索；搜查；寻求；
The police cordoned off the railway station to search for the escaped prisoner.
警察在车站戒严，搜捕逃犯。
3. be applicable to 适用的；适当的；可实施的；
The method is applicable to both metalized and conventional solid propellants.
这种方法既适用于普通的推进剂，也适用于含金属的推进剂。
4. in operation 运转，运行；
The machine is in operation.
机器正在工作。