How many single unit cubes are there in this Rubik's cube?

1. 27

The correct option is A 27
A Rubik's cube is made up of certain number of identical single unit cubes.We can see that the Rubik's cube has 3 horizontal layers and each layer has 9 single unit cubes.
Hence this Rubik's cube has $3\times 9=27$ single unit cubes.