og12-14:Sunpots,vortices of gas associated with strong electromagnetic activity, are visible as dark spots on the surface of the Sun but have never been sighted on the Sun's poles or equator.
这里的but前后时态可以不一致
og12－73：Combining enormous physical strength with higher intelligence,the Neanderthals appear as equipped for facing any obstacle the environment could put in their path,but their relatively sudden disappearance during the Paleolithic era indicates that an inability to adapt to some environmental change led to their extinction.
og D中的解释： Present-tense appear is needed to parallel Present-tense indicates作者: huangsiyan 时间: 2011-3-23 19:35
