1-D, because the content of the words (=meaning of the words) hinder the understanding of the talk.
2- B, evaluate means to measure the quality of something, in this case, you want to see how good your speech is by eliminating contradictions, logical flaws, words that can cause ambiguity and etc.
3- A, a feedback happens when the received piece of information generated by someone (let's call thissomeone who generates the first piece of information A ) is used as input to generate another piece of information from the recereiver (let's call the receiver B) which in turn can again be used as input to create another answer.
A -----------------------> B
^ v
|<--------------------------|
This scheme means: Information comes from A to B and then there is an answer from B which returns to A which can generate another answer to B and the cycle can go on until one part decides to finish it.