**Answer:**

The length of a side of the base is 20 centimeters.

The area of a lateral side between the bases is about 126.5 square centimeters.

**Step-by-step explanation:**

It's a rectangular prism with a total volume of 800 cu cm, and a height of 20 cm.

So, the base has an area of... 800/20 = 40 sq cm.

**The prism is a cube. **NO. If it was a cube, the base would be 400 sq cm (20x20), since the height is 20.

**The diagonal of the base is 4 centimeters.
** NO. with a base of 40 sq cm, it's impossible to have a diagonal of 4 cm. A diagonal would form a hypotenuse... and an hypotenuse is longer than the two other sides... an hypotenuse of 4 would mean for example sides of about 2 and 3... which gives 6 sq cm for the base, not 40.

**The length of a side of the base is 20 centimeters.** COULD BE. The base is 40 sq cm, it could have a side of 20 and the other of 2. Without knowing more about the prism than what's included in the question, we can't say YES and we can't say NO.

**The area of a base is 40 square centimeters.** Yes

**The area of a lateral side between the bases is about 126.5 square centimeters.** YES, since the height is 20, that would mean one side of the base would be roughly 6.325 cm... for a base area of 6.325 x 6.325 = 40 sq cm.