The answer is C is b/c sun exposure is completely natural unlike the followin answers.
Answer:
Dr. Reside's experiment can not be considered effective because his study has only treatment subjects group and lack of control group. That's why his study can be very good but not valid without control group.
In his study, he concluded that 80% children after therapeutic treatment decreased the activity level which can be true but not valid without control group because when he use control group in his study then we will be able to compare the normal or control group and treatment group. Then the study will be valid and effective as well.
Answer:
Many adults in their early twenties do choose to get married. However, in the world today it is more common for young adults to live as if married without actually taking the vows. So, your answer is legally recognized domestic union relationships that don't involve marriage. This is called Con-habitation.