"Single" joke

A girl walks into a supermarket and buys the following:
1 bar of soap
1 toothbrush
1 tube of toothpaste
1 loaf of bread
1 pint of milk
1 single serving of cereal
1 single frozen dinner
The checkout guy looks at her, smiles, and says,
`Single, HUH?`
The girl smiles sheepishly and replies,
`How`d you guess?`
He says, `Because you`re ugly.`