conundrum

conundrum [kə'nʌndrəm]
n.
1.(谜底含双关意的)谜语，双关谜
2.费解的难题，猜不透的难题

1.The answer to the conundrum is valuation .
这一难题的答案在于估值。

2.Another theoretical conundrum is entry to the auction .
另一个理论难题是进入拍卖。

3.That, however , is a lesser evolutionary conundrum than the one posed by her tiny brain , he asserts .
不过，沃波夫坚称，小的脑子引起的问题是比较大的演化谜团，这个问题比较小。