What hypothesis were the researchers testing in this study?

Sugar beet seedlings have a higher rate of fungal infection in heated soils.

Soils can be treated to reduce their ability to suppress fungal disease in seedlings.

The disease-suppressive properties of soils are due to the activities of soil microorganisms.

Sugar beet seedlings have a lower rate of fungal infection in disease-suppressive soils.

In an experiment examining the effects tai chi on arthritis pain, callahan (2010) selected a large sample of individuals with doctor-diagnosed arthritis. half of the participants immediately began a tai chi course and the other half (the control group) waited 8 weeks before beginning. at the end of 8 weeks, the individuals who had experienced tai chi had less arthritis pain that those who had not participated in the course.