ascertains , ascertaining , ascertained
If you ascertain the truth about something, you find out what it is, especially by making a deliberate effort to do so.
Through doing this, the teacher will be able to ascertain the extent to which the child understands what he is reading.
这样做,老师可以确定这个孩子对所读内容的理解程度。
Once they had ascertained that he was not a spy, they agreed to release him.
一查明他不是间谍,他们就同意了释放他。