The most common way to start a sentence would be d because you will have to know what your writting about
Answer:
Third sentence
Explanation:
In the first sentence, therefore is used for reasoning
ex: Therefore, dirty water is bad for the environment because it can make people sick
The second sentence is a run on sentence so it would not be correct.
The first is 1, the second is 4, the third is 3, the fourth is 5, and the fifth is 2.