Which of the following best defines the bold phrase their reasoning is sound I must admit

It highlights the most important parts of the authors aargh
It is based on evidence from the different sources
It’s thawed out and convincing
It includes an explanation of the authors opinion

None of the provided options accurately defines the phrase "their reasoning is sound, I must admit". The phrase indicates that the author acknowledges and accepts that the reasoning of the other party is logical and valid.