Fact 1: Agreenhouse is used to protect plants by keeping them warm. Fact 2: If the weather is warm, their temperature rises. Given the two facts above, how is a greenhouse used to protect plants?

Available options:
(1). prevent heat loss
(2). raising their temperature
(3). storing water
(4). reusing materials
(5). increase oxygen
(6). It helps them survive
(7). reflecting light
(8). evaporative cooling
Answer:
(2).