[单选题]
The wave equation for hydrogen has solution8nqy i6ea udkj(d n,5*s only if the threua +yp em )w/s7e2,sdae 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.
