Scientists use many different methods of investigation. When possible, scientists want to actually experiment or observe an event. Which method is useful when developing a scientific reasoning for an event that cannot be studied directly?
Conduct a field survey of bird populations in an area
Observe the effect of various fertilizers on corn crop yields
Use a computer model to study how the ocean liner Titanic sank
Use a wind tunnel to measure air drag on various types or automobiles

Observe the effect of various fertilizers on corn crop yields

Explanation:

I think I'm right

Observe the effect of various fertilizers on corn crop yields

Explanation:

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your answer is "the 1950's"