100 students take an exam and each gets an integer mark between 0 and 100, but 10 of the 100 students are absent on the day and receive a 0. The marks are stored in an R variable called marks and you are interested in calculating the average mark of the students that DID take the exam. Which of the following expressions can be used to compute this? For this question, you can assume that none of the students who attended the exam received a 0.多项选择题
A
a. mean(marks[marks > 0])
B
b. mean(marks[marks != 0])
C
c. mean(marks>0)
D
d. mean(marks[marks>=0])
E
e. sum(marks) / sum(marks > 0)
F
f. sum(marks[marks > 0]) / sum(marks > 0)
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