35. The widespread use of pesticides and herbicides has led to the........of groundwater in many oart of the world (corruption / infection / poison / contamination)
66. The root of the trees allow the water to go into the soil, that gradually rease it to flow down rivers.                                                                                    =>raising it
67. I get quite depressed when I think about the damage we are making to the environment.
                                                                                                      =>causing
68. Alike oxygen, which is chemically changes by our bodies into carbon dioxide, nitrogen is merely exhaled back into the air.                      =>Similar
69. I think will be suitable for the word because she has been working like a teacher for a long time.                                                                           =>Has worked
70. Passengers are required to arrive to the gate fifteen minutes befrore departure time.
                                                  =>arrive at