A mad scientist comes to you with a selection of specially made viruses and wants you to pick one to be unleashed upon humanity. Which do you choose?

You can choose to fight the mad scientist, but if you do it will cause an extinction level event.

Vampire A negative virus: This virus when unleashed will transform everyone with A negative blood into a vampire. They'll crave blood and they will only be able to come out at night. They will be able to get by on drinking animal blood but will much prefer human blood.

Sex virus: This virus when unleashed will cause everyone over the age of 20 and under the age of 70 to need sex to survive. As long as they get laid every 168 hours, they remain healthy. For every 168 hours that go by without sex, their health starts to deplete. If you go without sex for a month, you die. Weirdly it increases the size of a guy's genitalia by 40% and women's breasts by 40%. Pedophiles and anyone who commits sexual assault are rendered impotent.

Tech virus: This virus when unleashed causes the infected to take on robotic characteristics and allow them to mentally interact with technology. They also have to follow Isaac Asimov's "Three Laws of Robotics"

Animal virus: This virus when unleashed causes the infected to take on the animal characteristics of the last animal they touched. They'll still have their humanity but they'll have to be cautious not to let their animal instincts to take over

Zombie virus: This virus when unleashed gives the infected
50% chance of becoming an iZombie type of virus. Able to pass as normal as long as they eat a brain every 3 days. If they don't eat a brain, they slowly start to act like a stereotypical zombie. Once they get a brain in them, they return 'normal'
50% chance of becoming a stereotypical zombie one that is mindless and craves brains

Racial virus - This virus isn't what you think. No, it's more diabolical. This will turn the infected into a random race from fiction. Mentally they'll be human. Physically they'll look different. One person might become a Vulcan. Another might become a Wookie. Another might become a Frost Giant and so on. If what they become has an ability, they'll get that too

Body swap virus - This virus will cause the infected to body swap with anyone they look at, both infected and uninfected.

Emotion virus - This virus will cause the infected's emotions to become the opposite of what they're feeling.

Age virus - This virus will make the infected younger or older. Children up to the age of 10 suddenly become 30. Those 11-20 suddenly become 40. Those 21-30 become newborns. Those 31- 40 become toddlers . Those 41-50 become preteen age. Those 51-60 become teenagers. Those 70 and up become 20 year olds. They'll resume normal aging afterwards. They'll keep their memories

Animal virus - This virus doesn't effect humans but animals. It causes them to gain human level intelligence and take on a humanoid form

Thought virus - This virus will cause the infected's intrusive thoughts to become reality. However as the mad scientist doesn't want the Earth destroyed and if it is, he wants the credit for it, he's created a fail safe in the virus so that if anyone has such a thought, they are rendered comatose for a week.