The textbook states that researchers have replicated the conclusion that overweight children are not at risk for poor health outcomes as adults if they slim down to normal weight. what does the word "replicated" mean in this context?

This means that the conclusion has been found repeatedly.
If something is replicated, it is made again to look the same as the original did. In this case, the results that the researchers have gotten are the same as those some other researchers have come to before them. So, the results are the same - if overweight children lose weight, they aren't at risk for poor health when they grow up.

The answer should be a.