Answer:
A scientific hypothesis
Explanation:
For this research the null hypothesis would be;
H0 : the effect of exercise on social skills is zero, that is exercise does not influence social skills.
The alternative hypothesis would be;
Ha: the effect of exercise on social skills is not zero. That is exercise has effect on social skills.
A scientific hypothesis on the hand is the idea or explanation that you intend to test through study and experimentation. Thus, the believe by the researcher that people who become actively involved with an exercise program will show higher levels of socialization is just a scientific hypothesis that will be tested during the research and its not a null or alternative hypothesis.