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
Their valency is one and both belong to the third period
An embryonic stem cell is the first cell in the embryo, this is what creates a human and helps more cells to form.
Living things breath, feel, and smell.
Most living things have those characteristics.
I’m not 100% sure, but I hope I helped a bit.
The answer is.
propeller injury