Supernovae - Solution

1. B and E simultaneously, then D, then A, then C.
2. E, then D, then B, then A and C simultaneously.
3. B, then A, then D, then E, then C.
4. B, then D, then E, then A and C simultaneously.
5. The chronological order of A and B is the same in all frames of reference. The spacetime points A and B can be connected by an object or signal which travels slower than the speed of light. (In technical terms, A is in the future light-cone of B.) Therefore, B must happen before A in all frames.