25%
The probability that the remaining two children are boys is:
.50 X .50 = .25 or 25%.
This means that the probability that the daughter is the only female is 25%. Makes sense to me but I could be wrong (I think it's a multiplication but I don't really remember).
Several studies have investigated the relationship between intelligence and the degree of religious belief (excluding humanism), with most showing an inverse correlation between intelligence averages and the "importance of religion" to the testee.