Final answer:
The default subnet mask address of the given IPv4 address 11001111 11110111 11000111 00011101 is 255.255.255.0 (option d).
Step-by-step explanation:
The default subnet mask address of the given IPv4 address 11001111 11110111 11000111 00011101 is 255.255.255.0 (option d).
In an IPv4 address, the subnet mask is used to determine the network portion and the host portion of the address. The subnet mask consists of a series of 1s followed by a series of 0s. When we convert the given binary address to decimal format, we get 207.247.199.29. The default subnet mask for a Class C network, which this address belongs to, is 255.255.255.0.
In the given options, only option d matches the default subnet mask address of the given IPv4 address.