You assign an access key by including an . . . . . . . . option in the control’s caption or identifying label.

The correct answer is: A. &

An access key is a character that, when pressed together with the Alt key, activates a control on a web page. To assign an access key, you include an ampersand (&) followed by the character you want to use as the access key in the control’s caption or identifying label. For example, if you want to assign the A key as the access key for a button, you would include the following in the button’s caption: &A Button.

The other options are incorrect because they are not valid characters for an access key. The $, #, and @ characters are reserved for use in other contexts, such as currency symbols, hashtags, and email addresses.

I hope this helps! Let me know if you have any other questions.