The correct answer is A. accept.
The word “accept” means to receive something willingly or to agree to do something. In this case, the speaker is thanking the listener for agreeing to speak at the meeting.
The word “agree” also means to accept something or to consent to do something. However, it can also mean to have the same opinion as someone else. In this case, the speaker is not asking the listener to agree with them, but rather to accept their invitation to speak at the meeting.
The word “comply” means to do what someone asks you to do. However, it can also have a negative connotation, suggesting that you are doing something reluctantly or under duress. In this case, the speaker is not asking the listener to do something they do not want to do, but rather to accept their invitation to speak at the meeting.
The word “concur” means to agree with someone or something. However, it is typically used in a formal context, such as a legal or academic setting. In this case, the speaker is not using a formal tone, so the word “concur” would not be appropriate.
Therefore, the correct answer is A. accept.