Faculative
a. 允許的, 任意的, 兼性的, 偶發的
??? 情景例句
Dear Mr. Billet.
尊敬的比利先生。
What flights do you have from New York to London tomorrow?
明天從紐約飛往倫敦的有哪幾班機？
That's easy. I can do that tomorrow. I'll bring my drill.
那容易。我明天就做。我把鉆頭帶來。