〔R17〕  A noun there is of plural number,

                 Foe to peace and tranquil slumber;

                 Now any other noun you take,

                 By adding “s” you plural make,

                 But if you add an “s” to this,

                 Strange is the metamorphosis:

                 Plural is plural now no more,

                 And sweet what bitter was before.

〔譯註〕 有個名詞的複數形，

                  敵對平靜和安祥的睡眠；

                  這時你拿任何其他名詞，

                  加上 “s” 你就製造出複數，

                  可是如果你加個 “s” 到這個，

                  怪的是這個的變形：

                  複數的現在已經不再是複數，

                  而以前是苦的現在是甜的。

〔提問〕 If the word has five letters and rhymes (押韻) with “nightmares” (惡夢), what is it?

〔謎底〕  c____