Watch the video again. Choose the correct answers to complete the information below.Scientists noticed another bad thing that year. ( ______ ) levels in the air above Paris were ( ______ ) than usual. Plants normally take in ( ______ ) from the air, and release ( ______ ). However, the extreme heat reversed this process. This meant that the plants were no longer cooling and cleaning the air as well. 空1选项：1、Carbon dioxide2、Oxygen空2选项：1、higher2、lower空3选项：1、carbon dioxide2、oxygen空4选项：1、carbon dioxide2、oxygen