"Famers have a hard time learning how to work machinery" is false since learning is personal
"New technology needs to be made legal by the government" is false since it usually is prohibited instead of made legal when it is regulated.
"The new technology slows productivity." is surely false since the objective of the new technology is the exact opposite.
So the answer must be:
c. The high cost of purchasing modern equipment
New technology is always more expensive and farming machinery usually consists of heavy expensive equipment that many people might not have the money to buy.