by ohthatpatrick Thu May 10, 2012 9:14 pm
I think I interpreted (B) a little differently.
It's telling us that the viral infection makes children particularly susceptible to a bacterial infection in the middle ear.
Thus, it's no surprise that the antibiotics help these children get rid of the bacterial ear infection, since we're told that antibiotics are "effective in treating bacterial infections".
The original trickery was that in the 1st sentence, we're told that children with this viral infection develop a middle ear infection.
We probably all initially assume that the middle ear infection is also viral, but (B) suggests to us that the middle ear infection is bacterial.
Hope this helps.