As for today, because it is cold, a warm winter's coat I will wear. [Syntax]

The correct answer is "コートを". "コート" (coat) is the direct object of the verb "きます" (to wear), and "を" is the particle that marks direct objects. The preceding words "あたたかい" (warm), "ふゆ" (winter), and "の" (possessive/connecting particle) all describe and modify this "コート," specifying what kind of coat is being worn. Thus, "コートを" identifies the item of clothing.

正解は「コートを」です。「コート」は動詞「着ます」の目的語（もくてきご）で、「を」は目的語を示す助詞（じょし）です。前の言葉（ことば）が「コート」を説明（せつめい）しています。