Suggest reasons why we can live with one kidney, but we are born with two?

Drug categories matching. match the term in column 1 with the associated term in column 2. antihistamine antipsychotic analgesic antidiabetic anticholinergic beta-agonists anti-alzheimer ssri antianxiety corticosteroid cytotoxic antifungal antiviral quinolone cephalosporin rapid-acting insulin antiemetics anti-acidity antihyperlipidemics vasodilators antiarrhythmics calcium channel blockers beta blockers angiotensin ii receptor blockers diuretics digitalis preparations antiosteoporosis drug antiplatelet drug local anesthesia ipratropium simvastatin aricept dolasetron ciprofloxacin digoxin aripiprazole sotalol acyclovir valsartan hydralazine nsaid