Answer:
The answer is double helix.
Explanation:
In its natural state, each DNA molecule is actually composed of two single strands held together along their length with hydrogen bonds between the bases. Watson and Crick proposed that the DNA is made up of two strands that are twisted around each other to form a right-handed helix, called a double helix.
Hope this helps!! ;)
The answer to number 2 would be as the number of carbon carbon 2ble 2ble bonds increase, the melting point decreases
A is the answer. Hope that helped.