Question

What is this element?
A. beryllium B. nitrogen
C. lithium D. carbon

What is the mass number for the element above?
A.10  B.7  C.6  D.4

Answer 1

A lithium atom contains 3 protons in its nucleus. Notice that because the lithium atom always has 3 protons, the atomic number for lithium is always Z = 3. The mass number, however, is A = 6 for the isotope with 3 neutrons, and A = 7 for the isotope with 4 neutrons.
so most Likely your answer should be...

C. Lithium