Many students at a boarding school, including 6 just coming down with malaria,
went home during the second semester break. About 2 weeks later, 4 siblings of these
6 students (out of a total of 10 siblings) developed malaria. The secondary attack rate
among siblings was, therefore:
A. 4 ⁄ 6
B. 4 ⁄ 10
C. 4 ⁄ 16
D. 6 ⁄ 10 Answer this question correctly with working solution