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
Answer:
The cell is eukaryotic because it contains mitochondria.
nucleus
Explanation:
I think its true because the tornado is caused by the clouds.
Plants get their required nutrients from the soil.
Therefore, in Doppler Effect only the frequency and wavelength are changes and the wave speed does not change