Question

every autumn, the green leaves of summer change their color for a very specific reason. leaves use sunlight to perform a process called photosynthesis, which produces food for the trees. a green pigment in the leaves called chlorophyll helps make photosynthesis possible. as winter approaches, the days begin to get shorter, and photosynthesis becomes less efficient. sensing this, the trees begin a period of rest and chlorophyll decreases. as the green in the leaves disappears, other colors that were in the background all along become visible. what signals trees to begin a period of rest? 1 winter weather causes the green pigment, chlorophyll, to disappear. 2 the trees sense that the leaves are changing color in autumn. 3 the days get shorter and photosynthesis becomes less efficient.

Explanation:

The text states that as winter approaches, days get shorter and photosynthesis becomes less efficient. Sensing this, trees begin a rest period.

Answer:

1. The days get shorter and photosynthesis becomes less efficient.