... environment includes clean streets and highways with open spaces in cities for parks and playgrounds. Ideal surroundings mean landscapes free of junk and litter. They include regions of wilderness where ... of all other living things. Without conservation, all the resources necessary for life – air, animals, energy, minerals, plants, soil and water- would be damaged, wasted, or destroyed. Conservation ... what this process of immunization was and (40) ______ it could be used to control disease 31.a.invented b.discovered c.thought d.controlled 32.a.for b.in c.with d.of 33.a.began b.avoided...