The correct statement that causes a kinked demand curve is:
The oligopolist believes that competitors will match price cuts, but not price increases.
This belief leads to a demand curve that is kinked at the current price because if an oligopolist lowers its price, competitors will likely follow, resulting in a relatively inelastic demand curve for that price reduction. Conversely, if the oligopolist raises its price, competitors are unlikely to follow, resulting in a more elastic demand curve for the price increase. This creates the characteristic "kink" in the demand curve faced by the oligopolist.