1. Which is fastest

A, a olympic sprinter---B, a airplane---C, Light---D, a rocket

2. which is slowest

A, groundwater---B, a snail---C, a sloth---D, a human walking

3. which is in space but not on earth

A, ecosystems---B, galxies---C, power plants---D, magma

4. which is hottest

A, a bolt of lightning---B, the surface of the sun---C, death valley---D, the outer mantle

5.which is the same as 81²

A, 80*82-1 B, 80*82+1C, 80*81-1D, 80*81+1

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