Even if you have all the answers to all the questions, you need to have the following verbal communication skills if you want to impress an interviewer.
1. Listen carefully to what is being asked before you answer a question.
2. Don't interrupt the interviewer.
3. Let the interviewer lead the interview.
4. Speak clearly.
5. Use proper grammar.
6. Don't be afraid to ask for clarification if you don't understand a question. It may be more embarrassing to speculate and give an inappropriate answer.
7. Answer concisely.
8. Don't exaggerate.
The listening skills that you demonstrate in an interview are critical to your success, not only as a candidate but as a professional. If an interviewer asks a question twice, or seems to rephrase a question, you may have missed something.