点击下方单词,选择对的这个单词
形容词
1. 可选择的;非强制的If something is optional, you can choose whether or not you do it or have it.
1. possible but not necessaryleft to personal choice
形容词electivevoluntary
形容词compulsory
多通过句子记忆单词,而不是单独死记硬背。