The primary method in which two connected objects transfer energy by heat flow is conduction convection radiation all of the above

The correct answer to the question is conduction.

EXPLANATION:

Before coming into any conclusion, first we have to understand the modes of heat transmission which are known as conduction, convection and radiation.

Conduction is the process of transfer of heat from hotter part of a body to the colder part or a hot body to a cold body, in contact with each other, without any actual transport of material particles.

Convection is the mode of transmission of heat in which actual transport of particles will occur. The heating of water is an example of convection. In this process, the water particles which are present at the bottom part of the container will be heated first and becomes lighter. The lighter particle of water will go up and the top heavier particle will move downward. Again the same process will be repeated. In this way, a convection cycle will be produced.

Radiation is the type of transmission of heat in which heat will flow from one body to another body which are not in contact with each other without heating the intervening medium. The light coming from sun to earth is an example of radiation.

Here, two object are connected. Hence, the correct answer to this question is conduction.