Step 1: Identify the personalities.
Kennedy refers to John F. Kennedy, Indira refers to Indira Gandhi, and Palme refers to Olof Palme
Step 2: Find the shared feature.
Kennedy was a President, Indira Gandhi was a Prime Minister, and Olof Palme was also a Prime Minister
So options about all being Presidents or all being Prime Ministers are incorrect
The common fact is that all three were assassinated
Step 3: Conclusion.
Therefore, the correct option is All of them were assassinated