In the Context of the Various Strategies for Investing in Securities

In the context of the various strategies for investing in securities, the problem with market timing is that:

A) it is tough to consistently identify the timing and direction of changes in stock prices.
B) the returns are very low because stockholders invest in low-risk securities.
C) stockholders are required to purchase securities and hold them for a long period of time.
D) intensive research is required to find stocks that are undervalued in the market.