TASK DEFINITION: Given a scientific passage and an answer, generate a question for the given answer.
PROBLEM: Passage: In eukaryotic cells, the DNA is kept in the nucleus. The nucleus is surrounded by a double membrane called the nuclear envelope. Within the nucleus is the nucleolus. Answer: nucleus

SOLUTION: In eukaryotic cells, where is the dna kept?

PROBLEM: Passage: Blood cancers affect the production and function of your blood cells. Most of these cancers start in your bone marrow where blood is produced. In most blood cancers, the normal production of blood cells is replaced by uncontrolled growth of an abnormal type of blood cell. These abnormal blood cells are cancerous cells, and prevent your blood from performing many of its functions, like fighting off infections or preventing serious bleeding. Leukemia is a cancer of the blood or bone marrow. It is characterized by an abnormal production of blood cells, usually white blood cells. Lymphoma is a cancer of a type of white blood cell called lymphocytes. There are many types of lymphoma. Answer: white blood cells

SOLUTION: Lymphoma is a cancer of a type of what type of cells, called lymphocytes?

PROBLEM: Passage: Ecologists look at many factors that help to describe a population. First, ecologists can measure the number of individuals that make up the population, known as population size . They can then determine the population density , which is the number of individuals of the same species in an area. Population density can be expressed as number per area , such as 20 mice/acre, or 50 rabbits/square mile. Answer: number per area

SOLUTION:
How is population density expressed?