Answer:
c. 93.3%
Explanation:
The formula and the computation of the labor-force participation rate is shown below:
Labor-force participation rate = Labor force ÷ Adult population
where, 
Labor force = Employed people + unemployed people
 = 25 million + 3 million
 = 28 million
And, the adult population is 
= 25 million + 3 million + 1 million + 1 million 
= 30 million
So, the labor force participation rate is 
= 28 million ÷ 30 million 
= 93.3%