ascertain

柯林斯词典

1. V-T If you ascertain the truth about something, you find out what it is, especially by making a deliberate effort to do so. (尤指经过努力) 查明[正式]
Through doing this, the teacher will be able to ascertain the extent to which the child understands what he is reading. 通过这样做，老师将能确定这个孩子对他正在读的内容的理解程度。
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。