Boron occurs naturally as two isotopes. what is the difference between these isotopes?

Atoms that have the same number of protons but different number of neutrons are called isotopes. Boron exists in the form of two stable isotopes on the earth's crust. These isotopes are B10 and B11 (with ten and elven neutrons respectively)
Boron is an element which is found in the 2nd period of the periodic table. It is a naturally occurring element which is very hard to come by, because of being very rare. Turkey is the country where boron has been found the most and it is also the biggest producer of boron minerals. 

The answer is letter c