2. it could be double stranded DNA molecule or a ladder that is twisted.♀️ and I think 1. is covalent and hydrogen.
(dont worry I searched them up on google)
A ) adenine and thymine
DNA has two types of nitrogenous bases: purines and pyrimidines. Adenine and guanine are purines while cytosine and thymine are pyrimidines.
A purine always pairs with a pyrimidine. Hence, adenine in DNA pairs with thymine while guanine pairs with cytosine. This is done to maintain the constant width of the double helix throughout the length.
Each nucleotide base can hydrogen-bond with a specific partner base in a process known as complementary base pairing: Cytosine forms three hydrogen bonds with guanine, and adenine forms two hydrogen bonds with thymine. These hydrogen-bonded nitrogenous bases are often referred to as base pairs.
strands of phosphate sugar backbone with complementary nitrogenous base pairs bound into a double helix
Adenine pairs up with thymine, and cytosine pairs up with guanine.