Which of the following is TRUE about M&As$?$

a$.$ Managers' ego can sometimes get in the way of M&A decisions.

b$.$ About $80-90\%$ of M&As eventually succeed in practice.

c$.$ Firms engaging in M&As cannot diversify into businesses fast, compared to a case where they rely on another method of diversification.

d$.$ Compared to other methods of diversification, M&As are relatively less risky.