Which two properties do change with altitude?

As altitude increases, the amount of gas molecules in the air decreases—the air becomes less dense than air nearer to sea level. Thin air exerts less pressure than air at a lower altitude

b. the carbon cycle ensures living things have a source of hydrogen

answer: 20 percent

the fish culture has become a developing commercial practice in developing countries which is already prominent in developed countries of the world. the major fish protein demand is being supplemented in developing countries is   fishing to meet the needs of the growing population. therefore, in some developing nations, the percentage of animal protein from fish in the diet can be as high as 20 percent.