You can use ", ' or [].
The benefit is you can choose to have any of these characters inside a string without problems...
eg
x= '"' + "It's a nice day " + [" said the dog's fleas]

>Dear All,
>
>I would like to know that what is the difference between single quotation Mark and double. please logically justify the both why we use single quote and double quote.
>
>Yours truly,
>
>Nafees