单选题：How can we obtain the number of valid users in the system?

How can we obtain the number of valid users in the system?@[B](1)
A. grep -v ^$ /etc/passwd
B. cat /etc/passwd | wc -l
C. cat /etc/passwd | wc -w
D. cat /etc/shadow | wc -w



A.grep -v ^$ /etc/passwd
B.cat /etc/passwd | wc -l
C.cat /etc/passwd | wc -w
D.cat /etc/shadow | wc -w


答案：B