When he was set free after twenty years in prison, he was amazed ________ the changed world he found.
单词用法。be alnazed at/by对…很惊讶，惊异，如：We were absolutely amazed at his rapid recovery".他身体恢复得如此快，这令我们很吃惊。be amazed to do sth.惊讶的…，如：When I looked at my watch I was amazed to see that it Was well after six.我看表时惊讶地发现早过了六点。并无B和C这种搭配。