Identify each of the following compounds.
a. A gas with a sweetish odor that promotes the ripening of green fruit.
b. An unsaturated compound of the formula C7H8 that gives a negative test with bromine in carbon tetrachloride.
c. A compound with an ammonia-like odor that acts as a base; its molecular formula is CH5N.
d. An alcohol used as a starting material for the manufacture of formaldehyde.