Topic: Sequence of Tense,

Best Answer Explained in Below-:

The sentence "When the guests arrived, they ---- lunch" requires a verb form that aligns with the past tense context established by "arrived." The correct choice, C) "were having," is in the past continuous tense, which indicates an ongoing action that was happening at a specific point in the past.

The phrase "when the guests arrived" sets a temporal marker indicating that this arrival happened in the past. The use of "were having" suggests that the guests were in the midst of their lunch when they were interrupted by the arrival of someone. This implies a simultaneous action—while one action (the arrival of the guests) is complete, another action (having lunch) was ongoing at that moment.

In contrast, option A) "had" indicates a completed action in the past, while B) "have had" implies a present perfect aspect, and D) "have" is present tense, none of which would appropriately convey the intended meaning of an action that was ongoing during the moment of arrival. Therefore, "were having" is the only option that cohesively fits the narrative context, making it the correct choice.