Answer: C. narrow-based calls
Step-by-step explanation:
Narrow based calls would include calls from one industry. The mutual fund is an "High technology" firm which means that it is a narrow based fund for instance as it is interested only in one industry being the High Tech industry.
The manager should invest in Narrow based calls that focus on the sector if he anticipates that the market will remain flat for the sector. Narrow based Calls are more volatile because they are specific and with the volatility comes higher premiums to be charged.
Should he wish to make income against the portfolio, he should sell these knowing that the options will not be called as the market will remain flat.