Read the Paragraph Below and Answer the Questions That Follow

Read the paragraph below and answer the questions that follow.
(1) The solution to an important AIDS puzzle came from an unlikely source, video gamers. (2) For fifteen years, researchers at the University of Washington have been trying to understand the structure of the AIDS virus, knowing that this discovery would lead to better treatments, maybe even a cure. (3) In 2010, Seth Cooper, a computer scientist at the same university, created a video game called Foldit, the purpose of which was to encourage gamers to work on real scientific problems. (4) Hearing about Foldit, the frustrated scientists decided to ask gamers for help. (5) In three short weeks, the gamers came up with such good models that the scientists found their answer. (6) The scientists are thrilled, and the gamers loved using their skills for such a worthwhile project.
Which of the following sentences does NOT contain a transitional expression that indicates time?

A) Sentence 2
B) Sentence 3
C) Sentence 4
D) Sentence 5