The correct answers are: Option 1 and option 3.
Explanation- It is given that daily highy temperature doesn't vary much and it is only 1°C more than 10 years. So, it won't be the possible reason for simploid sickness and death. So it is not plausible to investigate the weather's effect(which is almost constant) using experiment. The other two factors i.e; parasite and herbicide can be investigated by experiments( taking dependent and independent variables for a hypothesis and checking the effect of factors under consideration). So option 1 and 3 both are correct.
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