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

Input: Consider Input: Passage: Pea plants are naturally self-pollinating. In self-pollination , pollen grains from anthers on one plant are transferred to stigmas of flowers on the same plant. Mendel was interested in the offspring of two different parent plants, so he had to prevent self-pollination. He removed the anthers from the flowers of some of the plants in his experiments. Then he pollinated them by hand with pollen from other parent plants of his choice. When pollen from one plant fertilizes another plant of the same species, it is called cross-pollination . The offspring that result from such a cross are called hybrids. Answer: cross-pollination

Output: What is it called when pollen from one plant fertilizes another plant of the same species?

Input: Consider Input: Passage: Immovable joints do not allow the bones to move at all. In these joints, the bones are fused together by very tough collagen. Examples of immovable joints include the joints between bones of the skull. You can see them in Figure below . Answer: immovable joints

Output: The joints that are between the bones that make up the skull are what kind of joints?

Input: Consider Input: Passage: During the systolic phase of the cardiac cycle, the heart is ________. contracting b. relaxing c. contracting and relaxing d. filling with blood 16. How do arteries differ from veins? a. Arteries have thicker wall layers to accommodate the changes in pressure from the heart. Arteries carry blood. Arteries have thinner wall layers and valves and move blood by the action of skeletal muscle. Arteries are thin walled and are used for gas exchange. Most of the hormones produced by the anterior pituitary perform what function? a. regulate growth b. regulate the sleep cycle c. regulate production of other hormones d. regulate blood volume and blood pressure 18. What is the function of the hormone erythropoietin? a. Answer: muscle
Output: Arteries have thinner wall layers and valves and move blood by the action of skeletal what?