Notes:
expose 〈…を〉〔日光･風雨などに〕さらす;
reflection 熟考，内省，黙想;
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Joke 1: What Happens to Gold
Professor: What happens to gold when it is exposed to the air?
Student (after reflection): It’s stolen!
Joke 2: I Don’t Know
Teacher: What three words are used most by students?
Student: I don’t know.
Teacher: That’s it. Correct!
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(by Yang Q.W. (1986) English Jokes. Taibei: Learning Publishing House. p40.)