A lot of people call AES as an algorithm because it adopts Rijndael as a Standard. However, AES is more specific so that all implementations of AES conform to the 'standard' and are therefore inter-operable - meaning they can talk to each other. One of the things that AES takes care is how diffusion is implemented. It is implemented as a combination of shiftrows and mixcolumns. The shiftrows is simply: a. permutation of data at byte level.
b. using many keys.
c. same as mixcolumns.
d. using substitution box.

The answer is option (a) permutation of data at byte level.

Explanation:

Solution

During the process of AES (Advanced encryption Standard) algorithm, these two steps shift rows and mix columns are two sub-steps of process, in which, shift row works on rows and basically shifts nth row by n-1 bytes to left side, that is, the first row will not shift at all, the second row by one place shift left, and apart from it mix columns works on columns. in this each column is transformed with a particular function, so these two steps are very different.