31. If the population is 300 million, with 70 million under the age of 16 and institutionalized, another 70 million not in the labor force, 10 million unemployed and 150 million employed, the labor force participation is _______.
(A) 6.67 percent.
(B) 69.6 percent.
(C) 50 percent.
(D) 23.3 percent.