so I choose to use the present perfect passive tense. Similarly, twenty people were injured when the explosion occurred - I am thinking of that moment in time in the past, so I choose to use the ...

The present perfect is the tense that we need in order to do this. Do you want me to make the salad for supper tonight? ~ I've already made it. It's on the table. I've just spoken to Jane.

When two things occurred in the past, the past perfect tense comes in handy to express them within a clause. In other words, unlike the present perfect tense which states an action that started in ...