There are several important information's already given in the question. Based on those information's the answer can be easily deduced.
In the first case,
The amount of chicken the chef cooks for 36 people = 9 pounds
Then
The amount of chicken the chef cooks for 1 person = 9/36
= 1/4 pounds
Now let us take the second case
The amount of chicken the chef cooks for 68 people = 17 pounds
Then
The amount of chicken the chef cooks for 1 person = 17/68
= 1/4 pounds
From the above deductions, it can be concluded that the correct option among all the options given in the question is the third option or option "C".