CFA Sample V2 Q.13 - Covered Call she, particular, recently, correct, protect

leadcfa

The client wants to protect her gains from owning a particular stock that has recently risen in value.
The right answer is that she can do it with a cover call strategy (writing the call on that stock).
How is that correct?
Wouldn’t that limit her upside rather than protecting her gains?

bluejazzy

premium from call short provides cusion for downside protection