Question

what type of bond holds the nitrogenous base pairs together?
a covalent bond
b ionic bond
c peptide bond
d hydrogen bond

question 8
which nitrogenous bases pair together in dna?
a a with g; c with t
b a with c, t with g
c t with t, a with g
d a with t; c with g

question 9
what type of bond holds the sugars and phosphates together in the dna backbone?
a metallic bond
b hydrogen bond
c ionic bond
d covalent bond

Explanation:

Question (First one: What type of bond holds the nitrogenous base pairs together?)

Nitrogenous base pairs in DNA (like A - T, G - C) are held by hydrogen bonds. Covalent bonds are for strong atom - atom sharing (e.g., in DNA backbone), ionic bonds involve charge - charge attraction, and peptide bonds link amino acids. So the correct bond is hydrogen bond.

In DNA, the base - pairing rule is adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). Option a has wrong pairs, option b has incorrect pairings, option c also has wrong pairs. Only option d follows the correct base - pairing.

The sugar - phosphate backbone of DNA is held together by covalent bonds (specifically phosphodiester bonds, a type of covalent bond). Metallic bonds are in metals, hydrogen bonds are between base pairs, and ionic bonds involve charge - charge interactions. So the correct bond is covalent bond.

Answer:

d. hydrogen bond

Question 8 (Which nitrogenous bases pair together in DNA?)