Which correctly punctuates an introductory element?

a) outside the house in the yard we saw a dog chasing our cat.

b)in room 210 there are 3 boys and 17 girls.

c)no we do not want to go!

d)on bus 18, there is a kind man named mr. cantucci.

Geoff bought a picture frame and took a picture with his parents because a) he wanted to be a notable athlete. b) he wanted to remember his trip always. c) he wanted to get into the hall of fame. d) he wanted a baseball player to sign it.