Astronomy current events question: jovian ring ripples

Astronomy 210L, Spring Semester 2011
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!)

Astronomy.com editors, "Forensic Sleuthing Ties Ring Ripples to Impacts," April 1, 2011
http://astronomy.com/en/News-Observing/News/2011/04/Forensic%20sleuthing%20ties%20ring%20ripples%20to%20impacts.aspx

Images from various NASA spacecraft have determined that ripples in the rings of Jupiter and Saturn were caused by:
(A) collisions with cometary fragments.
(B) interactions with nearby moons.
(C) sunlight along the equators of both planets.
(D) radio signals sent to and from Earth.
(E) strong magnetic fields.

Correct answer: (A)

Student responses
Sections 30678, 30679, 30680
(A) : 38 students
(B) : 7 students
(C) : 1 student
(D) : 1 student
(E) : 7 students