[单选题]
The wave equation fort: dr.9f z-7 f7gmdfhvw7ufr * hydro4u3v* cpm3 dyvoh:mu/gen 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.
