Question

Each element can have only one ID and Each page can have only one element with that ID.

Answer 1

Explanation:

please mention the whole question here

Answer 2

Explanation:

Since an ID is a unique identifier for an element you can only use this once and never again in another element.

<div id="idname"></div>

A class is different. You can use a class on any element and any number of times elsewhere in your document

<div class="classname"></div>