Select the correctly spelt word.

The correct option is registration.

Let's analyze the spelling of each option to identify the correctly spelled word:
1. refridgerator: This is spelled incorrectly. The correct spelling is refrigerator (without the letter 'd').
2. litrature: This is spelled incorrectly. The correct spelling is literature (missing the 'e' after 't').
3. registration: This is spelled correctly. It refers to the act or process of entering information into an official registry or list.
4. allegater: This is spelled incorrectly. The correct spelling is alligator (ends with 'or', not 'er').

Therefore, the only correctly spelled word among the options is registration.