1 、( 1) B

(2) C

2、﹙ 1. 1? 0.5+0.5? 0.8﹚? 2+ 1. 1? 0.8

=﹙0.55+0.4﹚? 2+0.88

=0.95? 2+0.88

= 1.9+0.88

=2.78 square meters

A: It takes at least 2.78 square meters to make this water tank.

Extended application

3. Solution: After cutting the small cube, the surface area of the remaining part is equal to the original surface area.

So surface area: 3? 3? 6=54 (square decimeter)

A: The surface area of the remaining part is 54 square decimeters.

Solution: Dig a small cube with a side length of 1 decimeter at the vertex of the cube. The areas of the upper, front and right sides of the cube are reduced by 1 cube respectively, and the areas of the three cubes are reduced by one * * *, but the surface area of the remaining part is the same as that of the original cube. 3? 3? 6 = 54 (square decimeter).