Type the access-list command that permits all packets sent from hosts in subnet 14.15.16.0/24. Use the ACL number 50 for the ACL rule.

(A) access-list 50 permit 14.15.17.0 0.0.0.255
(B) access-list 50 deny 14.15.16.0 0.0.0.255
(C) access-list 50 permit 14.15.16.0 0.255.255.255
(D) access-list 50 permit 14.15.16.0 0.0.0.255

access-list 50 permit 14.15.16.0 0.0.0.255 is the correct answer.

The syntax of the ACL command is:
access-list access-list-number {deny | permit} source [sourcewildcard]
Each standard numbered ACL has one or more access-list commands with the same number, any number from the ranges 1–99 and 1300–1999. Besides the ACL number, each access-list command also lists the action (permit or deny), and the matching logic (the IP addresses to permit or deny). In this case, the ACL permits all the IP addresses from the subnet 14.15.16.0/24 The wildcard mask (not subnet mask) allows standard ACLs to match a range of addresses. Instead of typing:
access-list 50 permit 14.15.16.0
access-list 50 permit 14.15.16.1
access-list 50 permit 14.15.16.2
access-list 50 permit 14.15.16.3
etc etc
access-list 50 permit 14.15.16.255
you can just use a wildcard mask to match all the addresses within that range with a single command.