Limescale
n. 水垢; 垢石
??? 情景例句
I'll be the leader.
我來當(dāng)指揮。
How much is it by air mail?
航空信要多少錢？
becomes so worn and unreliable that it eventually is not worth mending.
磨損太厲害，老得一點兒也不準(zhǔn)了，最終會不值得修理了。