Answer:
lack of diversification in the client's account
Step-by-step explanation:
As a brokerage firm, your immediate concern in this situation should be the lack of diversification in the client's account. This is an incredibly large amount of money and the client has 100% of it invested in a single stock. Seeing since it is a blue-chip company, chances of it being delisted or its price falling sharply are very low but still possible. Still having all your money in a single asset is extremely risky, and every client should be diversified in many assets in order to reduce the portfolio's overall risk.