Fill in the blank with the most appropriate word. The last days of the holiday ________ by rain.

The correct answer is: were spoiled.

The sentence is in the past tense, so the verb must also be in the past tense. The other options are not in the past tense.

• Was spoiled is the simple past tense of the verb “to spoil.” It is used to describe an event that happened at a specific time in the past. In this case, the event is the last days of the holiday being spoiled by rain.
• Are spoiled is the present tense of the verb “to spoil.” It is used to describe an event that is happening now or that happens regularly. In this case, the event is the last days of the holiday being spoiled by rain. However, the sentence is about a specific event that happened in the past, so the present tense is not appropriate.
• Have been spoiled is the present perfect tense of the verb “to spoil.” It is used to describe an event that happened at an indefinite time in the past and has an effect on the present. In this case, the event is the last days of the holiday being spoiled by rain. However, the sentence does not indicate that the rain had an effect on the present.

Therefore, the correct answer is were spoiled.