Answer:
b
Step-by-step explanation:
I think is B.
hope its help
2.21073919x10^23
Apply the Negative Exponent Rule. Negative exponents in the numerator get moved to the denominator and become positive exponents. Negative exponents in the denominator get moved to the numerator and become positive exponents.
corresponds to 
and 
(or 
, since 
).