Doorstone
n. 门槛石
🗣️ 情景例句
Hmm. It's probably nothing.
嗯， 也许没什么事。
After my core courses are finished, I'll be doing independent study.
在完成基础课程之后，我将作独立的研究。
I have just received a letter from my brother, Tim.
我刚刚收到弟弟蒂姆的来信，