______ is even more important is ______ as the earth cooled down, water began to appear on its surface.

A. What, that           B. That, what          C, That, that           D. What, what

 What is even more important is_____ the earth cooled down, water began to appear on its surface. 

A. that         B. that as          C. which             D. which as

Deserts, dry areas with _____ no vegetation, cover more than one-third of the Earth's land surface.

       A. surprisingly    B. eventually     C. permanently     D. virtually

      is even more important is              the earth cooled down, water began to appear on its surface.

A.When; that; when   B.What; whether; as   C.What; that; as     D.lt; whether; as

What is even more important is______ the earth cooled down, water began to appear on its surface.

A．that              B．that as            C．which            D．which as