What is the primary advantage of using a Fiestel cipher structure?

Select one:

a$.$ It significantly increases the key size, making it more resistant to brute$-$force attacks.

b$.$ It enables strong diffusion of plaintext bits across the data block, concealing patterns.

c$.$ It provides strong confusion by applying non$-$linear operations like substitution boxes.

d$.$ It allows for efficient decryption using the same operations as encryption, just in reverse order.