Why was the customer willing to buy 20 lighters in the end？

Why was the customer willing to buy 20 lighters in the end？
A.Because the salesman gave her a discount.
B.Because the only ‘problem’ of the lighter turned out to be a strong point: it’s childproof.
C.Because the customer was convinced of the benefits of the product.
D.Because the product was easy to carry.
正确答案：Because the only ‘problem’ of the lighter turned out to be a strong point: it’s childproof.；Because the customer was convinced of the benefits of the product.