Choose the option that correctly sequences the following sentences. 

1. People with severe gum disease are almost twice as likely to suffer from a heart attack or stroke.

2. However, one recent Belgian study found that when people with gum disease chewed food, bacteria were released into their bloodstream that could increase inflammation.

3. But researchers are still trying to find out if there is a cause-and-effect relationship.

4. Why this happens is yet unknown.

5. Even those with moderate gum problems have a higher rate of circulatory problems.