题型：填空题 通常人们面对面彼此交谈的语声，是靠______传播的．而在河边钓鱼时，人们最怕有人从旁边走过，因为鱼儿会被吓跑，这说明______和______也可以传声．一般来说声音在______中传播最快、在______中传播最慢．不特别强调时，空气中的声速一般就取______． 查看答案
题型：填空题 Jane: Hello, Mary!Mary: Hello, Jane! 46 Tom.Jane: Nice to meet you, Tom.Tom: 47 Look! Jane, this is my family photo.Jane: Oh, are these your parents?Tom: 48 They are my father and mother.Jane: 49 Tom: No, it isn’t. She is my uncle’s daughter.Jane: I see. She is your cousin. 50 Mary: Her name is Gina.Jane: Thank you. Bye.Mary: Bye.What’s her name?This is my brother,Nice to meet you, too.Yes, they are.I’m fine, thank you.What’s that in English?Is this your sister, Mary? 查看答案
题型：填空题 构成投资组合的证券A和证券B，其标准离差分别为14%和8%。在等比例投资的情况下，如果二种证券的相关系数为1，该组合的标准离差为11%；如果两种证券的相关系数为-1，则该组合的标准离差为3%。( ) 查看答案