What OSPF command, when configured, will include all interfaces into area 0?

What OSPF command, when configured, will include all interfaces into area 0?
A . network 0.0.0.0 255.255.255.255 area 0
B . network 0.0.0.0 0.0.0.0 area 0
C . network 255.255.255.255 0.0.0.0 area 0
D . network all-interfaces area 0

Answer: A

Explanation:

Example 3-1 displays OSPF with a process ID of 1 and places all interfaces configured with an IP address in area 0. The network command network 0.0.0.0 255.255.255.255 area 0 dictates that you do not care (255.255.255.255) what the IP address is, but if an IP address is enabled on any interface, place it in area 0.

Example 3-1 Configuring OSPF in a Single Area

router ospf 1

network 0.0.0.0 255.255.255.255 area 0

Reference: http://www.ciscopress.com/articles/article.asp?p=26919&seqNum=3