Ifndef
如果未定义
🗣️ 情景例句
Thanks, Mr. Bennett.
谢谢 ，Bennett先生。
He hears a nice tune. Now, he is listening to it.
他听到了美妙的旋律。现在，他在倾耳聆听。
Then he quietly goes into their bedrooms, and fills their stockings with small presents.
然后他悄悄地走进他们的卧室，给他们的长统袜装上小礼物。