The image below shows one of the earliest stages of dna replication. what is the enzyme labeled a?

Helicase

Explanation:

Helicase enzymes unzips double helix DNA into single strands where replication will occur. For the DNA to be replicated, there have to be single strands acting as template for the new strand being synthesized by DNA polymerase. Since DNA is in double stranded form, it has to be unzipped into single strands. This action is achieved by the DNA helicase enzymes. It breaks down the H-bonds between the nucleotide bases of the strands and also ensures that the tension of the unwinding is not tranferred down the strand (which would cause the double-strand to snap downstream).

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