Carbon dioxide :increased or decreased
why and when

During the day or in spring and summer, plants take up more carbon dioxide through photosynthesis than they release through respiration , and so concentrations of carbon dioxide in the air decrease. Then at night or during autumn and winter, plants reduce or even stop photosynthesising, releasing carbon dioxide back into the air. This is often called the natural carbon cycle.

just did the assignment and the answer was #1 +2 n

i do not get it   at all