Question: What is the gender of the majority of Vivo phone users?
SQL: SELECT T.gender FROM ( SELECT T2.gender, COUNT(T2.gender) AS num FROM phone_brand_device_model2 AS T1 INNER JOIN gender_age AS T2 ON T2.device_id = T1.device_id WHERE T1.phone_brand = 'vivo' GROUP BY T2.gender ) AS T ORDER BY T.num DESC LIMIT 1