Answer:
The correct answer would be a hydrogen bond.
The two strands of the DNA are held together with the help of hydrogen bonds formed between the nitrogenous bases or base pairs.
The adenine (A) base pairs or makes a hydrogen bond with thymine (T) and guanine (G) base pairs or makes a hydrogen bond with cytosine (C).
2 hydrogen bonds are present between the A and T whereas 3 hydrogen bonds are present between G and C.
D) largest mass extinction event in Earth's history
Explanation:
The cambrian era started following the pre-cambrian extinction
c it is c
also E
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extrinsic