Answer:
The disease has made the man insane, but he does not know it.
Explanation:
The main point of these two sentences(6 and 7) is that the man is insane without him knowing. This has to be clearly pointed out when the two sentences are combined.
1. The disease has made the man insane, but he does not know it.
This clearly has the same main point of the original two sentences. It is the most obvious choice.
2. Not known by him, the disease has made the man insane.
This is a little less clear. Even though it still works, it is not as effective as 1,
3. The disease has made the man insane he does not know it.
Now, this sentence does not make sense at all. It just smashes together the two sentences. This is called a run on sentence. There are two independent clauses(man is insane from disease, does not know) that are improperly put together..
4. Making the man insane, the disease is not known by him.
This sentence is very unclear. It makes you read it twice before you understand what it actually means. This is the most unclear and ineffective sentence.
The answer is 1. The disease has made the man insane, but he does not know it. This is the most clear and effective way to join the two sentences, plus it makes grammatical sense.
