Which statement is true about adding radicals with different indices (for example, √5 and ∛5)?

They can be combined into a single radical as long as the number inside the root (the radicand) is exactly the same.

They cannot be combined into a single radical because they represent fundamentally different mathematical operations and are not "like terms."

They can be combined by adding the root indices together to create a new combined root (for example, a 5th root).

They can be combined by multiplying the number inside the root by the index of the other root.