Ten years……………. a very long time for a person to spend in prison.AreWereIsHave been

The correct form to complete the sentence is "have been."

Explanation

The phrase "have been" is used here to indicate an ongoing situation that began in the past and continues to the present. In this context, the sentence suggests that spending ten years in prison is a significant amount of time, which reflects the speaker's perspective on the duration of imprisonment.

The other options do not fit grammatically or logically:

• "Are" would suggest a present state but doesn’t connect appropriately to the concept of time.
• "Is" indicates a state of being but fails to incorporate the aspect of duration.
• "Were" refers to a past state and doesn't align with the present context implied in the sentence.

Thus, the complete sentence reads: "Ten years have been a very long time for a person to spend in prison."