In a positive correlation,
a.

the independent variable is always negative

b.

an increase in the independent variable has a corresponding increase in the dependent variable

c.

the dependent variable is always positive

d.

a decrease in the independent variable has a corresponding increase in the dependent variable

Regarding a positive correlation, options B and D are correct because A positive correlation is a relationship between two variables that their values increase or decrease TOGETHER. An increase or decrease in one variable always predicts the same directional change for the second variable. That is why we can say is both B and D