What is fixed at the top of the solar cooker?

The cooker's internal ingredient was heated using the mirror's concentrated solar light. Therefore, the solar cooker will employ a mirror to focus all of the sun's rays at a single place.

Before responding, let's learn more about solar cookers. The only difference between a solar cooker and the typical kitchen cooker is that a solar cooker uses sunshine to provide energy to the materials within. The solar light will reflect from the sun to the cooker by utilizing a mirror.
We can focus all of the sun's beams to one location by employing the concave mirror. Concave mirrors focus all of the sun's beams at its focal point since we know that all of the sun's rays originate from infinity. The thermal energy of this focused light, which is utilized to cook the food in the cooker, is extremely high.
Hence, the correct answer is option A.