What is the reason that the sun becomes visible even before sunrise and even after sunset?

the reason of seeing the sun a little before the sunrise is

The sun is seen on the horizon for sometime even after sunset.

The sun is seen on the horizon a little before sunrise. OR The sun is seen on the horizon for sometime even after sunset.

The sun looks reddish at the time of sunrise and sunset.

The sun looks reddish at the time of sunrise and sunset.

The sun is seen on the horizon a little before sunrise.