The correct answer is: Lucinda's relationship is more likely to be stable compared to Jack's in the face of relationship problems.
Since Lucinda has a more open-minded and flexible attitude regarding romantic relationships, and believes that they can change and improve over time, she is more likely to overcome and resolve any issues that arise with her partner. On the other hand, Jack has more black-and-white, and inflexible beliefs about relationships. Due to this, Jack's relationship with his partner is less likely to be stable and recover easily from conflict and issues with his partner.