Which of the Following Will Lower a Portfolio's Beta

Multiple Choice

Which of the following will lower a portfolio's beta?
I. Diversify among different types of securities and across industry and geographic lines.
II. Add investments with low betas to the portfolio.
III. Hold more cash or Treasury Bills in the portfolio.
IV. Reduce the percentage of the portfolio invested in high beta securities.

A) I, II and IV only
B) II, III and IV only
C) I, II and III only
D) I, II, III and IV