Which of the following is the wildcard (inverse) versio…

Which of the following is the wildcard (inverse) version of a /27 mask?

A.
0.0.0.7

B.
0.0.0.15

C.
0.0.0.31

D.
0.0.0.63

E.
0.0.31.255

Explanation:
Wildcard masks (also known as inverse masks) are used within access control lists and OSPF network statements to identify a range of IP addresses. The wildcard
mask specifies how many bits in the IP address must be examined to consider the IP address a “match” for the condition. A zero bit in the wildcard mask indicates a
bit that should be examined in the IP address, while a one bit indicates a wildcard, or a bit in the IP address, that should not be examined. A /27 mask indicates that
27 bits (out of a total of 32 bits in an IPv4 address) are being used for network routing information, as follows:
11111111.11111111.11111111.11100000 (27 one bits, or /27)
To find the wildcard(inverse) version of this mask, the zero and one bits are simply reversed as follows:
11111111.11111111.11111111.11100000 (27 one bits, or /27)
00000000.00000000.00000000.00011111 (wildcard/inverse mask)
Converting this binary string back into decimalyields 0.0.0.31, which is the wildcard version of a /27 mask.
A much easier and faster way to determine a wildcard mask is to perform the following operations:
1. Put the regular mask in dotted decimal format — in this case, /27 is 255.255.255.224
2. Subtract the value of the last octet from 255 — in this case, 255 – 224 = 31
3. Set all other octets to 0, yielding a wildcard mask of 0.0.0.31
The remaining answers are incorrect, as they are wildcard versions of different masks as follows:

0.0.0.7 = /29 (or 255.255.255.248)
0.0.0.15 = /28 (or 255.255.255.240)
0.0.0.63 = /26 (or 255.255.255.192)
0.0.31.255=/19 (or 255.255.224.0)
Objective:
Infrastructure Services
Sub-Objective:
Configure, verify, and troubleshoot IPv4 standard numbered and named access list for routed interfaces

https://www.cisco.com/c/en/us/support/docs/security/ios-firewall/23602-confaccesslists.html#topic2