Select the INCORRECTLY spelt word.

Scaleable

The incorrectly spelled word is "Scaleable." The correct spelling is "Scalable."

Here's an explanation for each option:

1. Effervescent: This is the correctly spelled word. It refers to something that gives off bubbles or fizz, or has a lively and bubbly personality or character.

2. Unorganised: This is the correctly spelled word. It means lacking organization or not being arranged in a systematic or orderly manner.

3. Efficient: This is the correctly spelled word. It means being able to accomplish a task or achieve a goal with minimum waste of time, effort, or resources.

4. Scaleable: This is the incorrectly spelled word. The correct spelling is "Scalable," which means capable of being scaled or expanded in size, capacity, or scope.