〔R4〕   It's something of whose sharpness I fight shy.

                But I have to trim it by and by.

                It grows without either food or drink.

                But it's already long enough, I think.

〔譯註〕 它這東西，其銳利我避開。

                  可是，我得修它在不久的將來。

                  它增長不需食物或飲料。

                  但是它已經夠長，我想到。

　

                        註： fight shy of:  避開、躲開。

                                  by and by:  不久( =  before long)

〔提問〕 If it is a nail but not one to be driven with a hammer, then what is it?

〔謎底〕  f_________