3. A)
You are I am sure, telling the truth.
B) You are, I am sure, telling the truth.
C) You are, I am sure telling the truth.
4.

grammatically, i wanna say that b is correct because of the division of thoughts, it makes sense to me to add those commas where they are

laughter and happiness are an essential part of life. laughing releases the body's "feel good" chemicals. thus, it provides long or short term relief from stress and or anxiety. more or less, laughing strengthens social connections and provides an easy approach in social related situations.

moreover, there are many benefits of laughter and humor. it's as if they play the role of superhero to combat anxiety and depression, according to researchers. happiness and laughter is the best medicine for teen mental health.

what happens in the body also affects the mind. the positive changes in physical health also have profound an impact on mental health. we have a lot to gain from laughing! medical effects of laughter have continued to validate the pain-relieving effect and benefits of laughter.

scientists tell us that laughter and humor actually, believe it or not, lower blood pressure, reduce stress hormones and increase muscle flexion. there are many benefits to happiness and laughter, and they so happen to increase the circulation of antibodies in the blood stream and make us resistant to infections.

as stated before, laughing releases your body's "feel good" chemicals, and on a related note, negative stress can cause your body to release chemicals that weaken your immune system which makes you more likely to contract a disease. luckily, laughter reduces negative stress and prevents those chemicals from being released.

all in all, you may want to consider laughing as much as you can!