Answer:
Density is nearly 3 cabs per hectare
Explanation:
Given -
There are three three intertidal regions.
Area of each intertidal region is 
hectares.
Number of crab in the intertidal regions are as follows -
Intertidal region I - 7
Intertidal region I - 2
Intertidal region I - 6
Sum of crabs in all three regions is equal to
Total area of all three intertidal regions is equal to
hectares
Now density per hectare is equal to total population of crab divided by total area of all the three intertidal regions
Density 
Density is nearly 3 cabs per hectare
8. is more fertilizers as that is the thing ehich changes everything because without that nothing will change
9. is the colour of light or plant growth i am unsure sorry
The purpose of a dichotomous key is to identify organisms
Explanation:
A dichotomous key is a kind of a tool that guides to classify and identify different organisms.
This key as the name indicates - dichotomous- consists of two parts or options to identify a species.
The method utilizes a series of questions/answers with two possible outcomes.
Taxonomically, a dichotomous key is used to basically identify a species or an organism by its scientific name.
All of the natural elements like the plants, animals, birds, etc are identified using this key.
Types of dichotomous key includes nested, linked, branching tree etc.
