Which of the following statement is (are) correct ?

Question

$\begin{array}{1 1}(a)\;The\; electronic \;configuration\; of\; Cr\; is\; [Ar]3d^5,4s^1(Atomic\;no\;of\;Cr=24)\\(b)\;The\;magnetic\;quantum\; number\;may\;have\;a\;negative\;value\\(c)\;In \;silver \;atom,23\;electrons\;have\;a\;spin\;of\;one\;type\;and\;24\;of\;the\;opposite\;type\;(Atomic\;no\;of\;Ag=47)\\(d)\;All\;of\;these\end{array}$