1-11 Interpret symbols for isotopes

1-11-1. The symbol ¹³C or C-13 represents an atom with...
A. 13 protons, B. 13 electrons, C. 13 neutrons, D. 13 nucleons

1-11-2. Which of the following has the largest mass number?
A. ⁵⁶Mn, B. ⁵⁶Fe, C. ⁵⁶Cr, D. they all have the same mass number

1-11-3. How many neutrons does an O-18 atom have?
A. 8, B. 10, C. 16, D. 18