valid formula

例句：

1. 1. The new policy is valid for the next three months.
   新政策有效期为三个月。
2. 2. The argument was valid; it made sense.
   这个论点是有效的，有道理。
3. 3. The test results are valid only if they meet the standards set by the manufacturer.
   测试结果只有在满足制造商设定的标准时才有效。