Which of the following statements is true?

The First one, second and forth are false

and the 3 one is true

Explanation:

The DNA is doble stranded in a double helix structure. There are 5 nucleobases (adenine (A), cytosine (C), guanine (G), thymine (T), and uracil(U)), only the first 4 are present in the DNA whilist the U substitutes the T in RNA.

The DNA has deoxyribose sugar while RNA has ribose sugar, that's what gives the doble stranded and single stranded form respectively.

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.

every el niño cycle is different. every year.