[单选题]
The wave equation for hydro3ei+z.1 sreaff4a7k mgen5 r e8zzi.dtqu g-q*h*yn5(dl has solutions only if the three quantum numbers $n$, $l$, and $m_l$ meet certain conditions. One of these conditions specifies that n
A. can be any real number.
B. can be any non-negative integer.
C. can be any integer.
D. can be any positive integer.
