Boron consists of two stable isotopes, B-10 (10.01amu) and B-11 (11.01amu). The average atomic mass of boron is 10.81amu. Which ratio of the number of B-10 atoms to B-11 atoms in a typical natural sample is closest to the true value?
a) 1:3
b) 1:4
c) 4:1
d) 1:2