Choose thr word (a, b, c or d) that best fits each of the blank spaces.      

     Sometimes it is necessary to (13) _____ our habits. Saving energy is one illustration. If we can (14) _____ more energy, such as water and electricity, we can help keep the natural environment safe. Saving water, for example, helps preserve out rivers and reservoirs. If we usually take 10-minute showers, (15) _____ this case we should try to take shorter showers. When we go out, we (16) _____ remember to shut off electronic like televisions and computers. Turning (17) _____  the lights is another example of saving electricity. In short, remembering to help the environment, such as by saving energy, is one of our most necessary responsibilities.

          Sometimes it is necessary to (13) _____ our habits