______ we all know air is gas.A.AsB.WhichC.ThatD

We all know that it is very hard to ______ him to give his plan up.A．endeavorB．reduceC．ass

We can know from the news item all of the following EXCEPT that______.A．651, 000 workers l

To be a grown－up, it means we know all of the following EXCEPT______.A．what we"re good atB

Antarctic _____ we know very little is covered with thick ice all the year round. A．which B．that C．w

We can t emphasize ______ the importance of air and water for the survival of all species.

All we know about the origin of language is that men, unlike animals, ______ invented cert