QUESTION 90. (UPSC CMS 2019 PAPER 2 )

In a family of six (2 parents and 4 children), the youngest child catches measles infection. The
parents are immune to the infection. On 3rd and 5th day of the infection of the first child, the two
other children also suffer from measles. The secondary attack rate (SAR) of measles is:

(a) 33.3 %
(b) 40 %
(c) 50 %
(d) 66.6 %