Which of these links will validate in XHTML 1.0 Strict?

The DOCTYPE declaration is required:

Which elements are form elements?

Correct way to use a paragraph in XHTML?

Which are correctly formatted?

Fill in the blank for the 'rel' attribute used in the following

You have to add a list of products in a drop-down list. What will you use to group the identical products under a category name?

You have defined the following image in an XHTML document:

Which is incorrect about the relation between HTML and XHTML?

Which is not correct for a 'meta' tag?