(1)Cells, like any factory, need energy to operate. (2)Two different kinds of cellular power plants have evolved: some cells absorb energy directly from the sun, while others gather energy by eating other organisms that have stored it.
(3)Plants acquire energy directly from sunlight through the process of photosynthesis.
(4)In this process, molecules of chlorophyll or related pigments absorb photons from the sun.
(5)The photons’ energy is converted into chemical energy that the plant can use to grow and reproduce.
(6)In the course of this rather complicated chemical process, carbon dioxide and water from the cell’s surroundings are converted into glucose plus oxygen.
(7)The net effect of photosynthesis, then, is to remove carbon dioxide from the air, produce energy for the cell, and give off oxygen as a waste product.
(8)Animals, unlike plants, cannot convert the sun’s energy directly to food, and therefore must get theirs by eating plants or by eating animals that eat plants.
(9)The food you eat contains energy in the form of the bonds that hold its molecules together.
(10)After the food has been broken down, it is taken into the cells, where its energy is released by a process called respiration.
(11)This process allows molecules like glucose to combine with oxygen, thereby releasing the energy tied up in the molecular bonds.
(12)Its waste product is carbon dioxide, which you breathe out.
In sentence 7, the word net means
a. sensible.
b. final.
c. unlikely.
d. negative.