Naturally occurring
B consists of two isotopes, whose atomic weights are 10.01 and 11.01. The atomic weight of natural boron is 10.81. The % of each isotope in natural boron is:
(a) % of isotope of mass 10.01 = 20, % of isotope of mass 11.01 = 80
(b) % of isotope of mass 10.01 = 30, % of isotope of mass 11.01 = 70
(c) % isotope of mass of 10.01 = 50, % of isotope of mass 11.01 = 50
(d) None of these.