81. At some temperatures, the relative reactivities of 3°, 2°, and 1° alkane hydrogens in free radicalchlorination are in the ratio of 5:3:1. Thus, monochlorination of isopentane should produce thesepercentages of 2-chloro-2-methylbutane (a), combined 1-chloro-2-methybutane and 1-chloro-3-methylbutane (b), and 2-chloro-3-methylbutane (c):
(A) 8% a, 75% b,17%c
(B) 25% a, 45% b, 30%
(C) 29% a, 44% b,18%c
(D) 30% a, 35% b, 35% c
(E) 36% a, 43% b, 21%c