Answer:
the answer is b: to explain how light travels
Explanation:
The correct answer is A. This is the case of using comma before a coordinating conjunction <em>and</em> because it links two independent clauses. We can observe that there two parts of this full sentence and each part is independent from each other. Both of them have their own subject and verb. Therefore, we are using a comma before <em>and</em>.
This is an easy one, use the order of elimination for problems like these in the future, but the answer is (A).
B) forty - one is the correct one
