简答题The optimum proton to neutron ratios is_______when the strong nuclear force is largest. A、1:1 B、1:1.4 C、1:2简答题Photosynthesis is a chemical process through which plants, some protists and bacteria produce glucose and _________ from carbon dioxide using only light as source of energy. A、nitrogen B、oxygen C、hydrogen简答题Hydrogen has the best ________ conductivity. A、 thermal B、electric C、magnetic多选题A、 B、 C、简答题___________exists between nucleons when they are . A、 attracting strong nuclear force B、Repulsive strong nuclear force C、 attracting weak nuclear force简答题Less than __________ of biomass energy produced by photosynthesis in earth has been used. A、 1% B、 3% C、10%简答题Alpha-rays can't pass through ___________materials. A、air B、lead metal C、Oxygen简答题Where did the flammable ice come from? A、River bottom B、Ocean bottom C、Mountain top简答题Replacing coal and _______with hydrogen doesn't required major modification of existing technology and equipment. A、nuclear energy B、petroleum C、wind energy