Answer:
Step-by-step explanation: We have been given 4 expressions. We are asked to choose the expression that represents sum of cubes.
We know that sum of cubes is in form .
We can see that 1st and 2nd option has a negative sign. Therefore, these options cannot be sum of cubes.
Let us check 3rd and 4th options one by one.
We can rewrite our expression by writing terms as cubes:
Therefore, expression is a sum of cubes.
In 4th expression, we can see that . We cannot represent it as a cube. Similarly, we cannot represent as a cube. Therefore, 4th expression is not correct.