I believe the medulla is the answer.
Answer:
both genetic engineering and artificial selection allow humans to change a species so that its member are better suited for human needs. artificial selection selects for traits already present in a species, whereas genetic engineering creates new traits.
Explanation:
A covalent bond? Not sure how much detail you want, sorry
To find the Percent Composition of an atom, you use this formula:
Mass of element in the compound you're studying on ( in this case it's 5 since there is 5 Hydrogens) over the mass of the compound (which is here 79), Multiplied by 100 since you want a percent.
So we get:

So you get about:


So, the percent composition of Hydrogen in NH4HCO3 is 6.3%
Hope this Helps! :D