1.what are the five major trends/periods in u. s. natural resource and environmental policy? 2.what is the endangered species act? what are 'endangered species'? what are "threatened species"? how do species become listed as 'endangered' or 'threatened' under this law? what is involved in 'delisting' a species? 3. name three factors that go into the creation/designation of 'critical habitat'. 4.what is the nuclear weapons complex? list three major facilities in this complex which have been closed down or are slated to be closed down.5. define high level radioactive waste. define low level radioactive waste: what are the classes of llrw and how are they defined?