The correct answer is A. 1,3-butadiene.
1,3-butadiene is a conjugated diene, which means that it has two double bonds that are separated by one single bond. This type of structure allows for the delocalization of electrons, which results in a lower energy state for the molecule. This lower energy state is reflected in the IR spectrum as an absorption band at 3300 cm-1.
1-butyne and 2-butyne are both alkynes, which means that they have a triple bond. Triple bonds are very strong, and they do not allow for the delocalization of electrons. This results in a higher energy state for the molecule, and there is no absorption band at 3300 cm-1 in the IR spectrum.
Cyclobutene is a cycloalkane, which means that it is a ring structure with four carbon atoms. Cycloalkanes do not have any double or triple bonds, and they do not allow for the delocalization of electrons. This results in a higher energy state for the molecule, and there is no absorption band at 3300 cm-1 in the IR spectrum.