Question: How many teams were represented in the pair of motor races held on 18 and 19 April 2015 at the Bahrain International Circuit in Sakhir, Bahrain?
Sentence (from "2015 Bahrain GP2 Series round"): The 2015 Bahrain GP2 Series round was a pair of motor races held on 18 and 19 April 2015 at the Bahrain International Circuit in Sakhir, Bahrain as part of the GP2 Series.
Relevant evidence: Yes