If a stock portfolio is well diversified, then the portfolio variance:

1) will equal the variance of the most volatile stock in the portfolio.

2) may be less than the variance of the least risky stock in the portfolio.

3) must be equal to or greater than the variance of the least risky stock in the portfolio.

4) will be a weighted average of the variances of the individual securities in the portfolio.

5) will be an arithmetic average of the variances of the individual securities in the portfolio.

please provide explanations