Our train ____________________________ the drivers' strike.

In this context, the phrase "was delayed due to" accurately conveys that the train's schedule was altered as a result of the drivers' strike. The word "delayed" specifically indicates that the train may not be running on time, which is a common consequence of a strike affecting transportation services.

This choice effectively aligns with the situation where a strike can cause delays in operations, as it implies that the train is still in operation but will arrive later than originally planned. The term "due to" also connects the reason (the drivers' strike) directly to the effect on the train service.

Other options, while they present valid scenarios involving a strike, may imply different outcomes. For example, "was postponed due to" could suggest that the train service has been rescheduled for a later time rather than just delayed. "Was cancelled because of" suggests that the train service has been completely called off, which might not be necessary if it’s just facing delays. "Was affected by" is broad and does not specify the nature of the impact on the train service, leaving too much ambiguity. Therefore, "was delayed due to" is the most precise choice to capture the intended meaning in this context.