This is the 2435th most frequent Russian word.
подтверждают
"Confirm" or "verify."
In this sentence, 'подтверждают' is used to indicate an action of affirming or expressing readiness, showing the present tense of confirmation.
Они подтверждают свою готовность участвовать в проекте.
They confirm their willingness to participate in the project.
Here, 'подтверждают' is used to describe the function of evidence supporting or verifying a theory or assumption.
Данные исследования подтверждают гипотезу учёных.
The research data confirms the scientists' hypothesis.
In this context, 'подтверждают' is applied to represent the role of documents as validating or proving a claim or legal fact.