The method of heat transfer by which the sun energy reaches the earth is

Radiation

Explanation:

The heat transfer take place by three modes

1. Conduction

This type of heat transfer take place in the solid materials like metals. This heat transfer take place due to vibration of electron.

2. Convection

This type of heat transfer take place in the moving fluid like water, air etc.

3. Radiation

Every materials which having temperature above 0 K are emitting radiation. This type of heat transfer dominate at the high temperature.

We know that temperature of sun is so high so the heat transfer from sun to the earth is take place by radiation mainly.

its c) radiation