Final answer:
The C4+ ion has the highest bond order and thus the strongest bond among the given ions, according to MO theory.
Step-by-step explanation:
According to molecular orbital (MO) theory, the ion with the highest bond order among the options given (Li+, Be2+, B3+, C4+) would generally have the strongest bond. The bond order is a measure of the number of chemical bonds between a pair of atoms; the higher the bond order, the stronger the bond. Based on the provided information, we can determine that Li2 has a bond order of 1, while Be2+ has a bond order of 0.5. Since ions with higher charge have higher bond energy and bond orders, by extension, C4+, which is not explicitly listed but follows the same trend, should have the highest bond order and thus the strongest bond among the given choices.