Which of these sentences is not punctuated correctly?

Jonathan addressed the press conference on June 12, 2011.

Stephan has a younger brother and an older sister.

Sandy, was unhappy with her grades.

Jeremy was a quiet, studious, and hard-working child.

Question

Which of these sentences is not punctuated correctly? 

Jonathan addressed the press conference on June 12, 2011.

Stephan has a younger brother and an older sister.

Sandy, was unhappy with her grades.

Jeremy was a quiet, studious, and hard-working child.

anonymous · Answer

What do you think the answer is most likely NOT?

anonymous · Answer

Well, I think you can rule out A and D. So that leaves either B or C. I think it's most likely C though.

anonymous · Answer

the sandy one

anonymous · Answer

sandy ,pause, is upset with her grades.
sandy is upset with her grades.

anonymous · Answer

yep it is the sandy one

anonymous · Answer

I agree with Missy5