What did Roosevelt say in his speech in Chicago

A．By using satellite images, maps, etc.
B．By studying specific fanning methods.
C．By studying the variation of human population.
D．By analyzing the quality of crops.

A．By turning the intensity of sunshine into maps.
B．By analyzing the recent weather report.
C．By capturing the microwave radiation from the soil.
D．By analyzing information provided by ground observation centers.