重点讲解：
1. switch on 打开,开启(电灯等)；
He didn't bother to switch on the light.
他懒得去开灯XvIlo0^IR^XvE;e。
2. be exposed to 使暴露于；
They were exposed to radioactive fallout during nuclear weapons tests.
在核武器试验中他们暴露在放射性尘埃之下]nATJe7LM&fhU.。
3. send out 发出(信号、声音、光、热等)；
Like bats, they send out sound waves and make sense of their environment from the echoes they receive back.
像蝙蝠一样，它们发出声波，然后根据收到的回音来了解周围的环境yunTSxEh5q-z%]Ni#]。
4. convert into (使)改变；更改；(使)转变；
The signal will be converted into digital code.
信号会被转变为数字代码DA(J2AwhS7gyFLVfk。