Answer:
The correct answer is None of these choices are correct.
Explanation:
Crossing over doesn't occur only between heterozygous genes, it also doesn't happen only in some chromosomes and it never reduces de variation, otherwise, the crossing over is one of the main causes of variation among species.
Rock cycle- the prices in which rocks undergo in the earths crust, involving igneous instruction, uplift, erosion, transportation, deposits as sedimentary rock.
Tectonic cycle- the movement of large portions of earths crust (plates) the driving forces that move these plates are a combination of events that occurs within the earth.
Water cycle- the path of all water followers as it moves around earth in different states, water vapor, ice, water...
Carbon cycle- series of processes by which carbon compounds are inverted in the environment involving the incorporation of carbon dioxide into living tissue by photosynthesis.
Nitrogen cycle- series of processes by which nitrogen and is compounds are introverted in the environment and living organisms.
Phosphorus cycle-biochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere.
the answer is D Nucleus, which has genes that contain many chromosomes
