When you activate Raiders from a crisis card, do you activate each one individual or as a group in a sector?

For Example: There are 6 raiders, 2 vipers and 2 civilian ships in a sector. Do you:

A) Activate them all at once, so two raiders will attack vipers (Which they may or may not kill), two will destroy the civilian ships and two will move off to another sector (to attack other civilian ships

Or

B) You activate the raiders in that sector one at a time, so if all 6 raiders fail to kill the vipers, then the civilian ships are safe

Thanks

One at a time. Give them the chance to miss the Vipers.

To me, raiders are activated separatly, because of their killing priority order.

They fisrt attack the vipers and, only if there is no viper left, they will attack civilian ships. If no raider succed in destroying the vipers in their area, so end of the activation phase.