True or false: Portfolio diversification is affected by the volatility of the returns of the individual investments

Question:

True or false: diversification is affected by the volatility of the returns of the individual investments in the as well as by the correlation among the returns. Explain.
Portfolio
A portfolio is a grouping of financial assets such as stocks, bonds, commodities, currencies and cash equivalents, as well as their fund counterparts, including mutual, exchange-traded and closed funds. A portfolio can also consist of non-publicly...