(C) Organic search
A Channel refers to the source/medium from which the visitor was referred to your website. Device is not considered a Channel. The default Channels report in Google Analytics contains 10 Channels which are Organic Search, Direct, Social, Referral, Email, Display, Affiliates, Paid Advertising(CPC), Other Advertising and Other.
This question is a part of the Google Analytics Individual Qualification. You can get all the answers with detailed explanation for this exam in our Google Analytics Individual Qualification Exam Answers page.