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.
there are less than one-quarter that many
there are fewer than one-quarter as many
there are fewer than one-quarter of that amount
the number is less than one-quarter the amount
it is less than one-quarter of that amount 选C还是D呢,我觉得选D,答案选C,there be句型不是很不好嘛