Fill in the blank with the most appropriate word.
People go to the tomb of the Unknown Soldier to stand in silence for a minute to honor the memory of those who ____ in wars.

In the given sentence "People go to the tomb of the Unknown Soldier to stand in silence for a minute to honor the memory of those who were killed in wars," the most appropriate word to fill in the blank is "were killed."

The verb "were killed" is in the past tense and is used to refer to the action of being killed in the past. The sentence is talking about honoring the memory of individuals who lost their lives in wars, which is an event that happened in the past.

Option A, "is killed," is in the present tense and does not match the context of talking about past events. Option B, "will be killed," is in the future tense, which is not appropriate for discussing events that have already occurred. Option C, "was killed," is in the singular past tense and does not agree with the plural noun "those" in the sentence. Option D, "are killed," is in the present tense and is not suitable for referring to past events.

Therefore, the correct answer is "E. were killed."