Answer:
Option C. is correct.
Explanation:
According to Chargaff's rules, DNA (Deoxyribonucleic Acid) from any species of an organism should have purine and pyrimidine bases in the ratio 
This ratio is very important for solving the structure of DNA.
As per this rule, DNA is double-stranded, and covalent bonds between identical nucleotides hold the strands together.
So, Option C. is correct.
4. D since its basically the bottom one
It is only 10% efficient because the majority of the energy is converted. Some is lost in heat, some is not processed at all. Mostly a lot of energy is used to regenerate ATP.
Answer:
major evolutionary change
Explanation: