Astronomy current events question: D1 Herculis and general relativity

Astronomy 210L, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)

Robert Naeye, "Stellar Mystery Solved, Einstein Safe," September 16, 2009
http://www.skyandtelescope.com/news/59467082.html

According to researchers at Villanova University, why are the star orbits of the binary system D1 Herculis not obeying Einstein's general theory of relativity? Circle your answer below.
(A) Gravity from a previously undetected third star.
(B) The rotation axes of the stars are tilted over on their sides.
(C) Dense Earth-like planets orbiting very close in.
(D) The stars pass directly in front of each other, as seen from Earth.
(E) Matter is slowly being transferred from one star to the other.

Correct answer: (B).

Student responses
Sections 70178, 70186, 70200
(A) : 12 students
(B) : 35 students
(C) : 4 students
(D) : 6 students
(E) : 6 students