For a quadratic function, if the coefficients on the level and squared terms have the same sign and the explanatory variable is necessarily non-negative, what is the effect?

	a.	There is a turning point for values x>0.
	b.	There is a turning point for values x<0.
	c.	There is no turning point for values x>0.
	d.	There is no turning point for values x<0.