When drive-ins were at the height of their popularity in the late 1950's, some 4,000 existed in the united states, but today there are less than one-quarter that many.
(a) there are less than one-quarter that many
(b) there are fewer than one-quarter as many
(c) there are fewer than one-quarter of that amount
(d) the number is less than one-quarter the amount
(e) it is less than one-quarter of that amount