下列四组物质中，前者属于纯净物，后者属于混合物的一组物质是[ ]
A．天然气、空气
B．氯化钠、食醋
C．天然水、碘酒
D．墨水、大理石
答案：B
______ the Venice Film Festival, we are to include high-quality films, ______ who makes them.
A．In defence of; regardless
B．In the defence of; regardless
C．In defence of; regardless of
D．In the defence of; regardless of
下列各项中，（）是评价材料静强度的重要指标。
A.比例极限
B.弹性极限
C.屈服极限
D.强度极限
E.断裂极限
