Spectroscopy Reference(new window)
Rule 2, omit O, gives C7H14
7 - 14/2 + 1 = 1 degree of unsaturation.
Look for 1 pi bond or aliphatic ring.
The band at 1718 indicates a carbonyl, probably a ketone. The bands at 3000-2850 indicate C-H alkane stretches.
This is the structure. See if you can assign the peaks on your own.
Note that D and E are chemically similar enough that their peaks overlap.