The relationship that results when organisms in an environment rely on each other for resources.

The relationship is called mutualistic relationship

Symbiotic Relationships

It is the kind of relationship in which organism prefer to stay in association as either both or at least one of the organism benefit from such association in the ecosystem.  

There are three types of symbiotic relationship -  

a)Mutualistic relationship – In this relationship, both the organisms in association get benefit for example the plover and crocodile. The plover feed on meat particles stuck in the teeth of crocodile, there by cleaning the teeth. Both plover and crocodile are benefitted by such association.

b)Parasitic – Here only species is benefitted. For example deer tick lives on the deer and suck its blood. Only the tick is benefitted while the deer is harmed.

c)Commensalism – In this one species is benefitted while the other species is neither harmed nor benefitted. For example – the relationship between the Remora fish and the whales. The Remora fish get attached to the whales through its fins and eat the remains of food of the whale. In this way Remora is benefitted but there is no harm or lass to the whale.  

humans, along with other animals and plants, have linear chromosomes that are arranged in pairs within the nucleus of the cell. the only human cells that do not contain pairs of chromosomes are reproductive cells, or gametes, which carry just one copy of each chromosome.

the correct answer, according to e2020, is the second choice there is an occluded front in region a and a cold front in region b.