By 1910 the top ten industries included printing, malt liquors, tobacco cars and railroad cars. The introduction of these new top ten industries indicated

(a) a shift in consumer preferences toward luxury items.
(b) an increase in real incomes in the U.S., permitting people to purchase luxury items.
(c) a smaller percentage of total consumption expenditures on essential food, clothing and shelter.
(d) all of the above.