A junior high school is going to organize students to participate in three kinds of extracurricular activities: A, B and C. It is stipulated that 2 students in each class will participate in Class A e

A junior high school is going to organize students to participate in three kinds of extracurricular activities: A, B and C. It is stipulated that 2 students in each class will participate in Class A extracurricular activities, 3 students will participate in Class B extracurricular activities and 5 students will participate. (1) according to the analysis of the meaning of the question, it can be concluded that there are 40 people and 5 people participate in extracurricular activities in class C, so the probability is 540 =18;

(2) According to the analysis of the meaning of the question, it can be concluded that the number of students is 40, and the number of people participating in the activity is 2+3+5= 10, so the probability is14;

(3)① Prepare 40 small balls; Consistent with the class size, correct;

② Don't draw all the balls, which is wrong;

(3) suppose that the experimental ball has only two class A markers, three class B markers and five class C markers; The distribution is consistent and correct with the extracurricular activity group;

In order to increase the chance of contacting a certain kind of ball, it is wrong to put the ball into a transparent glass jar for observation.

So the correct operation is ① and ③.