A patent gives the inventor:. a. property rights for 10 years.
b. the right to use the invention until development costs are recouped.
c. exclusive right to manufacture, exploit, use, and sell the invention for a given time-period.
d. the right to keep the patented process but not the product for five years.

answer; with few regulations protected the prices of crops which made farmers leave their farms and migrate to the big cities to work in factories;

i think it's d because a "rythem" is a

1)a particular type of pattern formed by rhythm.

2)a strong, regular, repeated pattern of movement or sound.

3) the systematic arrangement of musical sounds, principally according to duration and periodic stress.

so, d mabye.