Why did Emperor Qin Shihuangdi work to increase farming?
He wanted to increase food surpluses for disasters.
He hoped to improve Chinese diets by increasing crop variety.
He wanted to use new lands to produce more food for trade.
He hoped to gain the support of poor laborers with jobs on farms.

He wanted to use new lands to produce more food for trade.

Explanation:

During his reign, Emperor shihuangdi need a lot of money for the construction of the wall of China along with strengthening military to sustain the attack from the barbarian. So, he felt the need to increase more trade in order to add additional fund for the government.

This is why he used a lot of unoccupied land and use it for farming. To accomplish this operation he also mandated around 700,000 people into forced labor to work on the agricultural land.

a.   it resulted in widespread unemployment.