In modern supermarkets,
a customer does not have to stand in long billing queues if they have purchased ten items or less as there is a separate, dedicated billing queue for such customers.
Error analysis:- Original sentence has 2 errors. 1.) Pronoun error. ""They" is wrong pronoun for "a customer"". 2.) "less " can't be used for countable nouns.
(A) a customer does not have to stand in long billing queues if they have purchased ten items or less
Incorrect. As mentioned above.
(B) customers do not have to stand in long billing queues if they have purchased ten items or less
Incorrect. Usage of less is wrong.
(C) a customer does not have to stand in long billing queues if purchasing ten items or lesser
Incorrect. Usage of lesser is wrong.
(D) long queues can be avoided by customers who purchase ten or less items
Incorrect. Usage of less is wrong.
(E) customers do not have to stand in long billing queues if they have purchased up to ten items
Correct.