In Which Situation Does an MP Have the Biggest Incentive

In which situation does an MP have the biggest incentive to cultivate a personal vote?

A) When the electoral system uses closed lists and district magnitude is large.
B) When the electoral system uses an open list and district magnitude is moderate.
C) When the electoral system uses an open list and district magnitude is large.
D) When the electoral system uses closed lists and the district magnitude is equal to the number of seats in parliament.