Does the gut flora affect digestion?

Yes.

Explanation:

Our bodies need different organs to regulate our bodily functions, and the gut is no different. The gut flora helps us digest and break down the food we eat, along with producing various enzymes that help to break down carbohydrates. Also, after the carbohydrates are broken down, they can pass through the gut wall into the blood (just a little fun fact). The gut also helps to benefit our immune system. One last bit of information is that an imbalance of bacteria and microbes in our bodies may lead to weight gain, high blood sugar, high cholesterol, and many other terrible issues. Please let me know if you still need help and I hope this made sense!

the answer is:

carbon dioxide