根据药量、下药深度、地形和土壤以及高空危险因素，并考虑周围的（），从而确定离炮点的安全距离。

A、野生动物

B、公共财产

C、树木及易燃物品

D、与救援人员之间的距离

Ali is a dealer in Persian rugs. As his business has been rather slow, he placed an advertisement in the Saturday edition of his local paper stating:‘Once in a lifetime opportunity to own a handmade Persian antique rug for only ￡1,500 – cash only. This is a serious offer – the rug will go to the first person who accepts it – offer valid for one day only – today Saturday.’When Bud saw the advert, he immediately posted a letter of acceptance of Ali’s offer in order to make sure he got the rug.Cil also saw the advert and after inspecting the rug offered Ali a cheque for ￡1,500, but he refused to accept the cheque and told her she could not have the rug.Later in the day, Das asked Ali if he would keep the offer open until he could get to his bank to arrange a loan. Ali agreed, but subsequently, when Ed offered to pay ￡2,000 in cash for the rug, Ali sold the rug to him.On Monday morning Bud’s letter arrived, and Das returned to complete his purchase of the rug.Required:In the context of the rules governing the creation of contracts, advise:

(a) as to the precise legal nature of Ali’s advertisement; (4 marks)