What is the meaning of the idiom "heart and soul"?

with full energy

The correct answer is with full energy. The idiom "heart and soul" means to do something with great enthusiasm and energy. It is often used to describe someone who is passionate about what they are doing and is willing to put their all into it.

The other options are incorrect. Very healthy does not have anything to do with the idiom "heart and soul." Mutual cooperation and with lethargy are both the opposite of the idiom "heart and soul."