Which statement about portfolio diversification is correct?

	a.	Proper diversification can reduce or eliminate systematic risk.
	b.	The risk-reducing benefits of diversification do not occur meaningfully until at least 15-20 individual securities have been purchased.
	c.	Because diversification reduces a portfolio's total risk, it necessarily reduces the portfolio's expected return.
	d.	Typically, as more securities are added to a portfolio, total risk would be expected to fall at a decreasing rate.