假设有scores表的设计如下：StudentID（学生编号）,Class（班级），CourseID（课程编号），Score（分数）
（1）查询参加过至少两门课程考试的学生各门课程的平均成绩，以下SQL语句正确的是
A. select StudentID,avg(score) from scores group by StudentID having count(studentID)>=2
B. select StudentID,avg(score) from scores group by StudentID where count(studentID)>=2
C. select StudentID,avg(score) from scores where count(studentID)>=2 group by StudentID
D. select StudentID,avg(score) from scores having count(studentID)>=2 group by StudentID
