Yes you're answer (b) is correct. hope I helped. :)
The answer is A. B is correct, C is a comma splice, and D is correct
He shot his arrow through the seven trees because it was a challenge. It was done to prove his strength, valor, and skill. Not only did it do that, but it also pierced a mountain, entered earth, made a circle and came through the other side and went back into Rama's quiver.
Dear Teacher,
I am super sorry on how i have behaved in your classes. I am ashamed of what I have done. I am sorry that I was always late to class. Starting from when you read this letter, I will start following all the rules of your class just like all the other students. I would love if we can start our relationship over and get to know each other again, from the right foot.
Love
your soon to be fav Student