Question: What is the percentage of students who get a "B" in the course "Computer Network"?
SQL: SELECT CAST(SUM(CASE WHEN T1.grade = 'B' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T1.student_id) FROM registration AS T1 INNER JOIN course AS T2 ON T1.course_id = T2.course_id WHERE T2.name = 'Computer Network'