I only have one reason but hope it helps!
Because without those bases pairing there <span>would be no structure of a DNA.</span>
Maybe water Ian nothing B because it’s not C
I think its the left one (sorry if im wrong)
Answer:
''The air high above the air is colder than air at the surface. The vapor rises until it reaches a low enough temperature and pressure to condense water vapor into water droplets and form a cloud. When vapor condenses into liquid or solid particles, it loses some of its energy to the air''. From Google PLz like Thx ! @BRAINLY
Explanation: