What does this code do?

Code:
 @media only screen and (max-width: 500px) {
    body {
        background-color: lightblue;
    }
}

A. If the browser window is smaller than 500px, the background color will change to lightblue:

B. If the browser window is larger than 500px, the background color will change to lightblue:

C. The background color will change to lightblue

D. Nothing happens

Answer: Option A