Which service style involves a customer taking food away from a food service outlet?
a.
buffet service
b.
cafeteria service
c.
carryout service
d.
counter service

C.  carryout service

Explanation:

A restaurant that is allowing their customers to take food away, if offering a carryout service, also known as take-out service.  That's for example when you go to McDonald's and then bring your order back at home to eat it.

A buffet service is when the restaurant offers a wide variety of dishes already prepared and you go to the buffet tables to fill your plate with a bit of this, a bit of that... oh and a double portion of that one!

A cafeteria service is like you have at school.  You form a line to get your food from series of stations (soup, main dish, dessert, drinks), putting your items in a tray then pay... and then hope to find an empty table to eat your lunch.

A counter service is when you go eat in a dinner for example, and you sit on a bench and eat on a long table, called a counter.  That's usually for a quick meal.

your word would be isle.

isle is an island or peninsula especially a small one.

if you add the letter "a" you get aisle, which is a passage between 2 rows of something like chairs, shelves, or something else.