Text-1 Read the text. Then choose the correct answer for questions 1-2

Read the text. Then choose the correct answer for each question below (17-20).
Producing food costs the earth dearly. First of all, to grow food, we clear the land, prairie, wetland, or forest. This always causes losses of native ecosystems and wildlife. Then we plant crops or graze animals on the land. The soil loses nutrients as each crop is taken from it, so fertilizer is applied.
Some fertilizer runs off, polluting the waterways. Some plowed soil runs off, which clouds the waterways and interferes with the growth of aquatic plants and animals. To protect crops against weeds and pests, we apply herbicides and pesticides, These chemicals also pollute the water and, wherever the wind carries them, the air. Most herbicides and pesticides kill not only weeds and pests, but also native insects, and animals that eat those plants and insects, finally, we irrigate, a practice that adds salts to the soil in many areas. The water evaporates, but the salts do not, so the soil becomes more and more salty, hindering plant growth. This process, carried to an extreme, can dry up rivers and likes and lower the water table of whole region.