The fact that being homozygous recessive for the ccr5 receptor protects people from being infected with hiv, thus causing an increase in the recessive ccr5 allele, is an example of

Positive natural selection

Explanation:

Positive natural selection is fundamental to adaptive evolution and it is characterized by its ability to be passed on, that is heritable, and beneficial to a population.

1: most common garden plants prefer loam — soils with a balance of different-sized mineral particles (approximately 40% sand, 40% silt, and 20% clay) with ample organic matter and pore space. however, some plants grow better in sandy soils, while others are well-adapted to clay soils.

2: available water capacity is the maximum amount of plant available water a soil can provide. it is an indicator of a soil's ability to retain water and make it sufficiently available for plant use. available water capacity is the water held in soil between its field capacity and permanent wilting point.

3: it is the same for all living things (plants and animals). it also includes very tiny organisms that our eyes cannot see. they are known as microorganisms, and include viruses, bacteria and fungi.

the answer is b. glad to .