The chemical bonds that hold the two complementary strands of the dna double-helix close to one another are

The DNA double helix is comprised of several nucleotides. The nucleotides are adenine, guanine, cytosine and thymine. Adenine and guanine are purines. Cytosine and thymine are pyrimidines. The purines present on one strand form a hydrogen bond with the pyrimidines on the complementary strand. The adenine forms a pair with thymine and the cytosine forms a pair with guanine on the complementary strand. This hydrogen bonding between the several nucleotides result in the force that holds the two complementary strands together.

what's the question ?

1. a host loses nutrients to a parasite

2. a parasite only benefits when the host is alive (cause if the host dies the parasite dies with it )

3. producers to consumers

4. the tapeworm is a parasite

5. they convert energy from the sun (photosynthesis)

6. sunflower-robin (i think im 80% sure)

7. producer

8. consumer

9. prey

10. fresh water snails ( cause the green algea is the producer and the snails are the primary consumers and the small fish consumer so is the big fish)