Easy. Answer is oxygen because it says which one was missing before any life was on earth. And in order to have life on earth you need oxygen!
:)
Answer:
D. all the sunshine in a lake
B. Tundra - only biome with snow
25%,1:3 This is due to the heterozygous condition to produce on homozygous long and one homozygous short then two heterozygous short.ie 1:2:1,but short is dominant and heterozygous short ate taken to be short ,thus modifying the ratio to 1:3,1:3 is 25%:75%.therefore homozygous long is 25%.
