Which one is offer

Which of the following, in the context of entering into a contract, constitutes a binding offer to sell a unique item of furniture?
A Placing an advert in a newspaper with a price attached
B Placing it on display inside a shop with a price attached
C Telling someone the price you may be willing to accept for it
D Telling someone you will reduce the marked price on it by 10%
(2 marks)

Why is answer not C but D?

There was another question in the same mock where it said quotation of price could be accepted to form binding contract. So why not here telling price would be enough?