制冷剂的()和体积质量应尽可能小。 ["黏度","温度","基数","相对分子质量"]
从规模上看上,()是规模局限在一座城市范围内的局域网网络 ["局域网","广域网","城域网","城生活网"]
保持l/2的标准转弯率转过135°要花多长时间(). ["1分钟","1分20秒","1分30秒"]
下塔回流比减小,则氮气纯度()。 ["降低","提高","不变","无法确定"]
局域网是与广域网相对应的网络系统,它的英文全称是() ["Local Area Network","Local Network","Local A’network","LocalInternet"]
请解释为什么远期合同既可用来投机又可用来套期保值?