natural           was          mankind          made             polluted           of

Environmental pollution is one of the most serious problems facing (1)......................... today. Air, water and soil are necessary to the survival of all living things. Badly polluted air can cause illness and even death. (2).........................water kills fish and other marine life. Pollution (3)............... soil reduces the amount of land for growing food. Environmental pollution also brings ugliness to man’s (4).....................beautiful world. 

Một gen dài 5100A⁰. Biết X= 400 nu. Tính số lượng nu mỗi loại  T, X, G ?