If a major solar storm (solar flare) reaches the Earth, which of the following are the possible effects on the Earth ?

1. GPS and navigation systems could fail.

2. Tsunamis could occur at equatorial regions.

3. Power grids could be damaged.

4. Intense auroras could occur over much of the Earth.

5. Forest fires could take place over much of the planet.

6. Orbits of the satellites could be disturbed.

7. Shortwave radio communication of the aircraft flying over polar regions could be interrupted.

Select the correct answer using the code given below:

Which one of the following is a reason why astronomical distances are measured in light-years?