which do you think is the best answer?

[eddkzk]

Measles is viewed in developed countries as a mild childhood disease....................... .
a- despite the fact that a vaccine has been available since the 1960s.
b- but it can leave children with lifelong disabilities.

I came across this question in an English test. The correct answer is 'b', but I don't get what is wrong with 'a'.

[Horsa]

The beginning of the staement "Measles is viewed in developed countries as a mild childhood disease..." is a positive idea. That is it is not a serious ailment. In (a) we have a contrasting word "despite". After this word we would need a negative idea but the fact that there is a vaccine is a positive idea so this does not fit. In (b) we also have a contrasting word "but". So once again we need a negative idea to contrast with the positive beginning and "it can leave children with lifelong disabilities" is indeed a negative idea so this answer is the right one.

I hope that helps you to understand.

[eddkzk]

Thank you.