Answer: client's age
Step-by-step explanation:
From the question, we are informed that a 70-year old client wants to invest in U.S. Treasury securities and that when performing the suitability determination, the client informs the registered representative that he is looking for after-tax income, liquidity, and to avoid market risk.
The client's age should be the least the registered representative should be concerned about. Rather, the representative should be concerned with the coupon of the recommended treasury securities and the tax bracket of the client for tax purposes.