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

Ex Input:
Passage: The pioneer species is soon replaced by other populations. Abiotic factors such as soil quality, water, and climate will determine the species that continue the process of succession. Mosses and grasses will be able to grow in the newly created soil. During early succession, plant species like grasses that grow and reproduce quickly will take over the landscape. Over time, these plants improve the soil and a few shrubs can begin to grow. Slowly, the shrubs are replaced by small trees. Small trees then are succeeded by larger trees. Since trees are more successful at competing for resources than shrubs and grasses, a forest may be the end result of primary succession. Answer: primary succession

Ex Output:
What's the term for the gradual progression from simple plants to larger more complex ones in an area?

Ex Input:
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

Ex Output:
In eukaryotic cells, where is the dna kept?

Ex Input:
Passage: Lymphocytes: B Cells, T Cells, Plasma Cells, and Natural Killer Cells As stated above, lymphocytes are the primary cells of adaptive immune responses (Table 21.1). The two basic types of lymphocytes, B cells and T cells, are identical morphologically with a large central nucleus surrounded by a thin layer of cytoplasm. They are distinguished from each other by their surface protein markers as well as by the molecules they secrete. While B cells mature in red bone marrow and T cells mature in the thymus, they both initially develop from bone marrow. T cells migrate from bone marrow to the thymus gland where they further mature. B cells and T cells are found in many parts of the body, circulating in the bloodstream and lymph, and residing in secondary lymphoid organs, including the spleen and lymph nodes, which will be described later in this section. The human body contains approximately 10 12 lymphocytes. Answer: lymphocytes

Ex Output:
What are the primary cells of adaptive immune response?