Final answer:
The verb form in the sentence is present progressive, which describes ongoing actions at the moment of speaking and is formed with 'am' plus the present participle 'agreeing'.
Step-by-step explanation:
The verb form in the sentence 'I am agreeing with what you say' is present progressive. The present progressive tense is used to describe actions that are currently ongoing at the moment of speaking. It is formed with the present tense of the verb 'to be' (am/is/are) followed by the present participle of the main verb (-ing form). In this case, 'am' is the present tense form of 'to be' and 'agreeing' is the present participle form of the verb 'agree'.