The following types of glial cells (supportive cells) are responsible for helping to synthesize myelin, the insulation of axons: in the central nervous system (CNS) and in the peripheral nervous system (PNS.)

Oligodendrocytes and schawn cells.

Explanation:

Oligodendrocytes are form of gilial cells that is found in the Central nervous system. Oligodendrocytes secrete Myelin sheath around the axon of nerve fibres. They provide support and insulation to the Central nervous system.

Schawn cells are types of gilial cells found in the peripheral nervous system. They are also called neurilimma. They produce myelin sheath around the axon of neurons. They support nerve regeneration .

the correct answer is - d. china has a large and growing population.

the fact that china has a large (the biggest) population, and it is still growing, doesn't hinder the agriculture production in the country. in fact, it can for increased production in the agriculture, since there's more labor force, as well the sheer mass of people produces lots of scientists that come up with new inventions as to how to improve this sector. nice example is the inner mongolia region in china, in general dominated by the gobi desert, but few scientist came up with a nice idea as to how to make the region productive by using plants that are very resistant to droughts, so lots of people have been employed, and the region is becoming greener and greener each year, and the production of food in this region is also increasing.

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.