It has been found that major plant diseases and insect outbreaks are less likely to occur in a natural field than on a conventional farm because

In conventional farming practices, use of pesticides, kill both useful and harmful insects indiscriminately. Therefore, insect outbreaks are often seen in conventional farms

Fertilisers are used in conventional farming to increase yield. The increase in crop yield will consequently increase the diversity of pests

In natural field, the biodiversity sustains a complex system which checks and balances insects at a manageable levels

Both (a) and (c).