Which of the following events will result in a decrease in the population of butterflies?
1. Increase in the population of birds
2. Increase in the supply of plant fertilisers
3. Reduction in the number of green plants
4. Increased use of insecticides by man on gardens and green belts
A1, 2 and 3
B1, 2 and 4
C1, 3 and 4
D2, 3 and 4