Why my answer is wrong?

6 years ago

"Running is now very popular with teenagers in many countries both as a sport and as a way of keeping fit. (1) ... if you only run twice a week, you (2)... to wear good shoes. (3) ... is a lot of choice in running shoes, so decide how (4)... you can afford to pay for your shoes, then find a pair that fits you (5)... ."

5. A good B best C better D well

In the text above I had to choose between some adjectives. I have chosen best. My intuition told me, "Don't be an idiot. choose и best". I did like she told me, but I was wrong as the key section of the book said "d well".

Please explain me why I have to choose "well" rather than "best" or "better" in order for me not to make this mistake anymore.

Thank you!