Answer: C. Liquidity.
Step-by-step explanation:
The Investor has a long term time frame and desires to earn the market rate. For this to happen, financial vehicles catering for her needs would need to be locked up for a longer period of time for example 5 years before they allow withdrawals.
She however, wants to be able to withdraw yearly. This would mean that some of her positions would either need to be liquidated yearly or would have to pay a significant yearly payout.
As earlier mentioned, longer term instruments are usually locked up for long periods to be able to get the market rate. If the investor needs a yearly withdrawal from her positions, getting it from locked up positions will be a Liquidity challenge. The positions won't be easily sold and could attract a hefty fee to be liquidated and because they are locked up, they will not pay out yearly either.