【名词&注释】
课堂教学(classroom teaching)、中小学(primary and middle school)、重要作用(an important role)、课外活动(extracurricular activities)、重要途径(important way)、学生全面发展(students ' all-round development)、兴趣爱好(interests and hobbies)、全面发展教育(all-round development education)、等差数列(arithmetic progression)
[单选题]6,18,( ),78,126
A. 40
B. 41
C. 42
D. 44