Boron Has Two Isotopes: B-10 and B-11, with Masses of 10.013

Boron has two isotopes: B-10 and B-11, with masses of 10.013 amu and 11.009 amu, respectively. The relative atomic mass of boron is 10.81 amu. Which statement best describes the percent abundance of the isotopes of boron?

A) It contains more B-10 than B-11.
B) It contains more B-11 than B-10.
C) It contains equal amounts of B-10 and B-11.
D) There must be a third isotope of boron.
E) A mass spectrum of boron is necessary to answer this question.