Please teach me the way of writing of this kanji. [Syntax]

The correct answer is "書(か)き方(かた)" (kakikata). This sentence uses the pattern "V-方(かた)" (how to V / way of V-ing). To form this, the verb stem is used. The verb "書(か)く" (to write) has the stem "書(か)き". Thus, "書(か)き方(かた)" means "the way of writing". This correctly completes the phrase "この漢字(かんじ)の書(か)き方(かた)" (the way to write this kanji). "漢字(かんじ)" and "の" are already in the sentence, connecting "この" and the noun phrase. "を" is the object particle that comes after the full noun phrase.

正解は「書き方」です。「V-方」は「Vのしかた」という意味を表す名詞で、動詞の「ます形」の語幹に接続します。「書く」の語幹は「書き」なので「書き方」となります。「漢字」と「の」はすでに文中にあり、「を」は目的語の「書き方」の後ろにくる助詞のため不適当です。