49. I was under the impression that the tickets were sold out a long time ago.

点睛

be under the impression that...意为“认为，觉得”，该种表达不常见，因此是本句的难点。其实它相当于think或者have the feeling that...。如：
I was under the impression that he was kind. 我的印象中他挺善良的。
I'm under the impression that language is complex. 我觉得语言挺复杂的。
I am under the impression that it will rain in the afternoon. 我觉得下午会下雨。