点击下方单词,选择对的这个单词
点击下面链接下载与本句相关的学习资源，包括PDF教材和音频练习，方便课后复习：
1. the act of producing offspring or multiplying by such production
Synonym: generationmultiplication
2. the spreading of something (a belief or practice) into new regions
Synonym: extension
3. the movement of a wave through a medium
多通过句子记忆单词，而不是单独死记硬背。
