Extensive agricultural cultivation from 1870 to 1910, as described by

Extensive agricultural cultivation from 1870 to 1910, as described by Hughes and Cain (2011), meant that

(a) there could be no increase in agricultural output per man hour.
(b) the percentage increase in acreage under cultivation and the percentage increase
in agricultural output was roughly the same.
(c) the proportion of the labor force in agriculture steadily increased.
(d) all of the above were true.

ANSWER

(b)