Which vitamin is synthesized by bacteria in the human intestine?

Which blood vessels carry blood away from the heart?

What is the name of the theory that explains the origin of the universe?

What is the primary source of energy for Earth's climate system?

Which instrument is used to measure humidity?

What is the main cause of earthquakes?

What is the term for the loss of biodiversity in an ecosystem?

Which hormone is responsible for the fight-or-flight response?

Which organ regulates blood sugar levels in the body?

What type of blood cells help the body fight infections?

Which bird is known for its ability to mimic human speech?