General acceptance of 3-D films may prove hard to come by as the experience of three decades ago indicated.

Differences in positions adopted by oxygen and hydrogen...

单项选择题Differences in positions adopted by oxygen and hydrogen atoms account for variations in the crystalline structure of different forms of ice.

Many politicians find that they can no longer afford th...

单项选择题Many politicians find that they can no longer afford the luxury of a personal chauffeur.