Which of the Following Is a Run-On Sentence

Which of the following is a run-on sentence?

A) We are looking for an applicant who has five years of experience in the information technology field and who can work well with others.
B) Many celebrities post comments on Twitter this allows them to share their thoughts with millions of people instantaneously.
C) Cathy assigned many office-related tasks to Sarah, an intern from the university's business department.