Read the following passage, then choose the correct answer to questions

Plants supply man with food clothing, and shelter- his most important needs. Many of our most useful medicines are also made (26)_________plants. In addition, plants add beauty and pleasure to our lives. Most people enjoy the smell of flowers, the sight field of waving grain, and the quiet of a forest. Not (27)_______plants are helpful to man. Some species grow in fields and gardens as weeds that choke off useful plants. Tiny hits of pollen from (28)_______plants cause such (29)_________as asthma and hay fever. Other plants destroy millions of dollars (30)_______of crops yearly.

 

Many of our most useful medicines are also made (26)_________plants.