What are the ten systems of the human body?

All the organs and processes of the human body belong in one of ten anatomical categories. They are (in alphabetical order): Circulatory, Digestive, Endocrine, Excretory, Integumentary (skin), Muscular, Nervous, Reproductive, Respiratory, and Skeletal

Months that begin on a Sunday will always have a Friday the 13th."

Should you be rude in Tibet?

By U.S. customs, perhaps so! In the country of Tibet, it's good manners to stick out your tongue at your guests.

"A 95-mile-long underground river flows beneath Mexico."