Why do people like sad music vocabularies.

1、mammals 哺乳動物
意思：Any warm-blooded vertebrate having the skin more or less covered with hair; young are born alive except for the small subclass of monotremes and nourished with milk.
例句：In 2006, seeds were collected directly from trees or removed from mammal faeces.
2、lactation 哺乳
意思：The period following birth during which milk is secreted.
例句：The data related to late pregnancy and to lactation were analyzed separately.
3、circumstance 情況
意思：A condition that accompanies or influences some event or activity.
例句：Under the circumstances I cannot allow the request.