Correct Answer: 1980 and 1981

Solution : It is obvious from the graph.
In the year 1981, it changed from 30 to 35 (Increase)
Percentage change in production = $\frac{5}{30} \times 100$ = 16.67% increase
In the year 1982, it changed from 35 to 20 (Decrease)
Percentage change in production = $\frac{15}{35} \times 100$ = 42.86% decrease
In the year 1983, it changed from 20 to 25 (Increase)
Percentage change in production = $\frac{5}{20} \times 100$ = 25% increase
In the year 1984, it changed from 25 to 15 (Decrease)
Percentage change in production = $\frac{10}{25} \times 100$ = 40% decrease
In the year 1985, it changed from 15 to 30 (Increase)
Percentage change in production = $\frac{15}{15} \times 100$ = 100% increase
Hence, the correct answers are 1980 and 1981.