Astronomers Studying a Transiting Exoplanet Can Detect Other Nontransiting Planets

Multiple Choice

Astronomers studying a transiting exoplanet can detect other nontransiting planets in the same system by

A) timing the interval between transits.
B) taking spectra of the star as the planet transits.
C) measuring microlensing of the transiting planet.
D) Directly imaging the planet during a transit.