Every student of a certain school must take one and only one elective course. In last year, 1/2 of the students took biology as an elective, 1/3 of the students took chemistry as an elective, and all of the other students took physics. In this year, 1/3 of the students who took biology and 1/2 of the students who took physics left school; the chemistry students did not leave, and no fresh students came in. What fraction of all students either took biology or physics?	Choices.
A) 7/12
B) 4/9
C) 5/9
D) 1/4
E) 2/3
Lets pick smart numbers. Total number of students: 12   Biology (1/2): 6   5/9hemistry (1/3): 4   Physics (1/6): 2   After leaving school   Biology: 4   5/9hemistry: 4   Physics: 1   New Total number of students: 9   Biology and Physics: 5   Answer 5/9 or 5/9
<result>C</result>
Every student of a certain school must take one and only one elective course. In last year, 1/2 of the students took biology as an elective, 1/3 of the students took chemistry as an elective, and all of the other students took physics. In this year, 1/3 of the students who took biology and 1/2 of the students who took physics left school; the chemistry students did not leave, and no fresh students came in. What fraction of all students either took biology or physics?