Answer:
B. Fewer people are needed to weed because of herbicides.
Explanation:
Herbicides are chemical substances specifically used to control the widespread growth of weeds i.e unwanted plants. Using herbicides has been useful in eradicating the weeds that pose a great threat to agricultural productivity.
Since chemical control (herbicides) has proven to be a faster and effective method, fewer people are needed to involve in the physical control of weeds i.e. weeding. Hence, the use of herbicides has affected agricultural productivity by helping to reduce the amount of laborers.