The structures along with their codes are given below.
For Compound A:
# of ¹H signals: 3 (as both side chains from carbonyl positions are same)
# of ¹³C signals: 4
For Compound B:
# of ¹H signals: 3 (the two methyl groups of isopropyl are equivalent)
# of ¹³C signals: 4
For Compound C:
# of ¹H signals: 2 (as both side chains from carbonyl positions are same)
# of ¹³C signals: 3
For Compound D:
# of ¹H signals: 3
# of ¹³C signals: 4
