Sffd
abbr. step-function frequency discriminator 階躍函數鑒頻器
??? 情景例句
but I have work to do.
但我有工作要做。
I'm ashamed. I couldn't tell you my love.
我真的不好意思,愛你在心口難開呀。
Some of the things were hundreds of years old.
展出的一些東西已有數百年的歷史了。