You are given four samples, containing one compound from each pair below. For each sample you can use only one spectroscopic technique, ${?}^{13}C$ NMR$,$ IR$,$ UV$-$Vis, MS $($not exact mass$)$ or optical rotation to examine it$.$ Furthermore, each technique may only be used once. Which technique would you use for each of your samples? Briefly explain your answers stating specifically what you would observe that would allow the two compounds to be distinguished.

a

c$.$

d$.$