I agree—at least, I suppose I do
I agree that something ought to be done
I always welcome criticism so long as it is sincere
I am absolutely bewildered
I am afraid I am not familiar enough with the subject
I am afraid I cannot suggest an alternative
I am afraid I've allowed you to tire yourself
I am afraid I must confess my ignorance
I am afraid you will call me a sentimentalist
I am always glad to do anything to please you