Given a scientific passage and an answer, generate a question for the given answer.

Input: Consider Input: Passage: Plasma cells are activated B cells that secrete antibodies. Antibodies are large, Y-shaped proteins that recognize and bind to antigens. Plasma cells are like antibody factories, producing many copies of a single type of antibody. The antibodies travel throughout the body in blood and lymph. Each antibody binds to just one kind of antigen. When it does, it forms an antigen-antibody complex (see Figure below ). The complex flags the antigen-bearing cell for destruction by phagocytosis . Answer: antibodies

Output: What do you call large, y-shaped proteins that recognize and bind to antigens?

Input: Consider Input: Passage: There are three types of mechanical waves. They differ in how they travel through a medium. The three types are transverse, longitudinal, and surface waves. All three types are described in detail below. Answer: three

Output: How many types of mechanical waves are there?

Input: Consider Input: Passage: Along with the skin, the integumentary system includes the nails and hair. Both the nails and hair contain the tough protein, keratin. The keratin forms fibers, which makes your nails and hair tough and strong. Keratin is similar in toughness to chitin, the carbohydrate found in the exoskeleton of arthropods. Answer: keratin
Output: What is the name of the protein that is found in hairs and nails?