Sentence correction

I need help correcting each of these sentences. The punctuation is what I am looking for mostly.

1. The argument was clear; No citizen was to be deprived of its rights.

2. The woman that drove the car wore a red dress.

4. The speaker felt that many discoveries were the result of man's ingenuity.

5. The man was seen; but no one could identify him.

6. Some medications can be harmful, therefore one should be well informed.

7. If the truth were known the company would have been investigated.

I have an idea for some but wanted to make sure!