Your question was –
If the digit in the units place follows a pattern of 8, 4, 2, 6 then the numbers are the in the ascending order of the squares of which of the following number?

A few days ago I take part an exam where I have faced this GMAT questions and my answers option were –

a. 2
b. 4
c. 6
d. 8
e. None of the above

I have answered as my Correct answer is =  d

Because of this following Explanation:

For solving this question, first we will have to find out the squares of each of the options
at least upto a power of 5.
Squares of 2 in ascending order = 2, 4, 8, 16, 32
Squares of 4 in ascending order = 4, 16, 64, 256, 1024
Squares of 6 in ascending order = 6, 36, 216, 1296, 7776
Squares of 8 in ascending order = 8, 64, 512, 4096, 32768
From the above results, we can see that the digit in the units place of the squares of
number 8 in the increasing order of their powers follows the given pattern i.e. 8 4 2 6.

Hence, the correct answer is option d.

Hope you have got your answer.
Thanks.