[单选题]
If an element of atomic number 15 has an nbclvyt7 y9/8ish: t6 2lasl rh(alnksf ,4:l7ok6nvn;otope of mass number 32,
A. the number of neutrons in the nucleus is 15.
B. the number of neutrons in the nucleus is 17.
C. the number of protons in the nucleus is 17.
D. the number of nucleons in the nucleus is 15.