A platypus...

• A. Lays eggs

• B. Has ten sex chromosomes
• C. Has venom sacs
• D. Can detect electrical fields through its bill

Answer: All of the above.

Yes, the males actually have venom sacs in their hind legs. And for those who are frustrated that humans can't seem to figure out the mere two sex chromosomes we have, the platypus has ten.

Check out this article for more interesting information about the recent mapping of the platypus genome (don't worry, it's dumbed down for people like me).