Identify the DID WHAT in the following sentences.
Astronomers have recently announced the discovery of additional planets within our solar system. These planets are located within a zone of the solar systems that would allow liquid water to form. Could there be life on these planets? Scientists are investigating this question by using NASA's Kepler telescope.
A. astronomers discovered additional planets
B. Could there be life on these planets?
C. astronomers are using NASA's Kepler telescope
