6. Propose one structure each for compounds that meet the following descriptions:

a. CsHs with IR absorptions at 3300 cm^-1 and 2150 cm^-1

b. C4H8O with strong IR absorption at 3400 cm^-1

c. C4H8O with strong IR absorption at 1715 cm^-1

d. C8H10 with IR absorptions at 1600 cm¹ and 1500 cm^-1