I是开，代表in (启动)；O是关，代表out（断开）；
例如We had a day out in the country.
You should look out for yourself from now on.
从现在起你应该多为自己着想。
No one could have foreseen things would turn out this way.
谁都没有预料到事情的.结果会这样。
The new test should aid in the early detection of the disease.
新的化验应该有助于早早检查出这种疾病。
