Answer:
Maybe they both have valence electrons and can be used in chemical reactions. I could be wrong, I don't have any exact answers.
Explanation:
As long as the equation in question can be expressed as the sum of the three equations with known enthalpy change, its 
can be determined with the Hess's Law. The key is to find the appropriate coefficient for each of the given equations.
Let the three equations with given be denoted as (1), (2), (3), and the last equation (4). Let 
, 
, and 
be letters such that 
. This relationship shall hold for all chemicals involved.
There are three unknowns; it would thus take at least three equations to find their values. Species present on both sides of the equation would cancel out. Thus, let coefficients on the reactant side be positive and those on the product side be negative, such that duplicates would cancel out arithmetically. For instance, 
shall resemble the number of 
left on the product side when the second equation is directly added to the third. Similarly
Thus
and
Verify this conclusion against a fourth species involved- 
for instance. Nitrogen isn't present in the net equation. The sum of its coefficient shall, therefore, be zero.
Apply the Hess's Law based on the coefficients to find the enthalpy change of the last equation.
Answer:
<em>The correct option is B) a gradual change of the traits of a species over time</em>
Explanation:
The theory of natural selection explains the gradual changes which occur in the population of a species over time. According to natural selection, those organisms which are better adapted to live in an environment survive and pass on their traits to their offsprings. As a result, the traits of a species tend to change over time through the process of evolution. Evolutionary changes do not occur rapidly, instead, they can take many years to occur.
2.26%, 26.8%, 2 2/5, 2.62, 271%
Hope this helps! :D
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