Which among the following is an optional Keyword?

Answer: Option D

This question asks about keywords used in SQL queries. Let's break it down:
Keywords are special words that tell MySQL what to do in your query. Some keywords are essential, while others are optional.
DISTINCT is a keyword that removes duplicate rows from your result set. It's not optional, it's necessary if you want unique values.
ALL is a keyword that's usually used with quantifiers like "EXISTS" or "NOT EXISTS". It's optional because you can often write your query without it.
AS is a keyword that lets you give a temporary name to a column or table. It's optional because you can often use the original name, but it makes your queries easier to read.

Therefore, the correct answer is:
Option D: Both AS and ALL
Both AS and ALL are optional keywords.