everybody enjoys fresh cut flowers around his house．few people know how to keep them for as long as possible．

A．Because

B．Since

C．While

D．If

病人表现一般体力活动稍受限，活动后心悸、轻度气短、休息时无症状是心功能几级

A．Ⅰ级
B．Ⅱ级
C．Ⅲ级
D．Ⅳ级
E．Ⅴ级