天然气密度值的大小与（）有关。
A.压力
B.温度
C.压力、温度
D.压力、温度和气体组成
参考答案：D
About ______ of these books ______ sold out. [ ]
A. two thirds; have
B. two thirds; has
C. two third; have been
D. two third; has been
这个导向箭头是何含义？（）
A．指示向右转弯或掉头
B．指示直行或右转弯
C．指示直行或向右变道
D．指示直行或掉头
