実践！英文速読-5

  Trees give off oxygen which is essential to animal life. In the past few
decades, the need for wood has increased dramatically.

　スラッシュは関係代名詞、前置詞の前、カンマに入れます。

　Trees give off oxygen/ which is essential /to animal life. In the past few
decades, /the need for wood has increased dramatically.

　「木は酸素を放出する、それは不可欠だ、動物にとって。過去、数十年で、木に対する需要は増えてきている、劇的に。」