Note how this question has little to do with the passage. Often you will see questions like this on the MCAT. This is a simple, straightforward vocabulary question. The bonds between each compound are covalent. One might get confused and misunderstand the question to read inter-molecular bonds—those between different molecules—as opposed to the bonds within a molecule.

The oxygen atom in water has two lone pairs, though they are not as often drawn into depictions of the molecule as they are in nitgrogenous molecules, such as ammonia. They, along with the two bonds formed with hydrogen in stable water, make up the satisfied octet of oxygen.

The incorrect statement is a property of ionic compounds rather than covalent. Recall that electronegativity is a measure of the ability of an atom to draw electrons to itself. Ionic compounds are formed by elements with very different electronegativities, since elements with different electronegativities will tend to form positive and negative ions (that is, they give away or gain electrons easily). In contrast, covalent bonds are formed by elements which are close in electronegativity and could exist as stable free molecules. All other statements are true of covalent compounds.

The suffix -yne tells us that this is an aklyne and contains a carbon-carbon triple bond. Ethyne has the stongest carbon-carbon bond because it has the shortest bond length. It is important to remember that as the bond length gets shorter, the bond strength increases, and vice versa. 

O₂ has a nonpolar covalent bond. Nonpolar covalent bonds are bonds formed between atoms that have the same (or nearly the same) electronegativity. Since both oxygen atoms have the same electronegativity, they will have a nonpolar covalent bond between them. 

The intramolecular bonds within a water molecule are polar covalent bonds. O-H bonds are polar covalent since there is more electron density around the oxygen atom than there is around the hydrogen atom, making the oxygen atom slightly negative and the hydrogen atom slighty positive. This polarity allows for intermolecular hydrogen bonding; water does not exhibit intramolecular hydrogen bonding.

This bond is not ionic since the oxygen does not completly steal the electron away from the hydrogen (the electronegativity difference between the two atoms is between 0.4 and 1.7 on the Pauling scale).

 is an ionic compound, while  is a nonpolar covalent compound. Remember that polarity results from a difference in the electronegativities of the atoms involved in the bond. Too great of a difference will result in an ionic bond; two of the same atoms will have zero difference, resulting in a nonpolar bond.

, , and  contain polar covalent bonds. In the first two, oxygen will carry a slight negative charge, leaving sulfate and phosphorus with slight positive charges. In , chlorine will carry a slight negative charge, leaving the carbon slightly positive. In  and , symmetry helps to balance the polar bonds, resulting in an overall nonpolar molecule, even though the individual bonds are nonpolar.

Covalency is a form of electron sharing that lets an atom fulfill the octet rule. The sharing may be unequal, in which case the more electronegative species more strongly attracts the electrons than the weaker, less electronegative species, creating a polar covalent bond. In the Lewis dot model, however, we draw the electrons in freeze-frame, equally distributed between the various atoms.

A sigma bond is a single covalent bond, involving an electron pair located between the two bonding atoms. A pi bond occurs when the p orbitals above and below the bonding atoms overlap, or when the p orbitals to the left and right overlap. In any covalent bond, the first bond formed is a sigma bond and any additional bonds must be pi bonds. Initial orbital overlap always comes from the sigma, or s, subshell; subsequent overlap comes from the pi, or p, subshells.

This question is testing your ability to draw Lewis dot structures and your knowledge of how resonance effects bond length. The N-O bond with the greatest pi-bond character will be the shortest; thus, we are looking for a double- or triple-bond between nitrogen and oxygen.

Hydroxylamine () only contains single bonds, which have the least pi-bond character.

The nitrite and nitrate ions both have a double bond between the nitrogen and oxygen, but also one or more single bonds between these elements. This means that, because of resonance, the N-O bonds in these molecules will be averaged and our average bond order will be somewhere between single and double. Nitrate will have one double bond and two single bonds, for an average bond order of 1.33. Nitrite has one single bond and one double bond, for a bond order of 1.5.

The nitrosyl ion, however, will contain a triple bonds between the nitrogen and oxygen atoms, giving it the greatest pi-bond character. This bond will contain more energy and be shorter than the bonds in the other answer options.