Read each sentence to find out whether there is any grammatical error in it. The error, if any, will be in one part of the sentence. Mark the part with the error as your answer. If there is no error, mark ‘No error’ as your answer (Ignore the errors of punctuation, if any). The G20 summits are convened (1)/under a system of rotational presidencies (2)/and is selected from (3)/a different regional grouping of countries (4).