The intelligence scores of adopted children are least likely to correlate positively with the intelligence scores of their:

The correct answer to this open question is the following.

Your question is incomplete. You missed the end of the question that is “…their adopted siblings during:”

Although you did not attach options for this question, we can say the following.  

The intelligence scores of adopted children are least likely to correlate positively with the intelligence scores of their early adulthood.

Scientists and sociologists know that adopted children usually have different personalities than their adoptive parents for obvious reasons. That is why during infancy, parents can exert a positive influence on children by exemplifying the kind of behaviors they want the children to have in social life. This aspect can determine the way adoptive children can develop or learn that set of new skills or personalities taught by the parents.  

question - in 1827, john walker, a druggist in a small english town, tipped a splint with sulphur, chlorate of potash, and sulphid of antimony, and rubbed it on sandpaper, and it burst into flame. the druggist had discovered the first friction-chemical match, the kind we use to-day. it is called friction-chemical because it is made by mixing certain chemicals together and rubbing them. although walker's match did not require the bottle of acid, nevertheless it was not a good one. it could be lighted only by hard rubbing, and it sputtered and threw fire in all directions. in a few years, however, phosphorus was substituted on the tip for antimony, and the change worked wonders. the match could now be lighted with very little rubbing, and it was no longer necessary to have sandpaper upon which to rub it. it would ignite when rubbed on any dry surface, and there was no longer any sputtering. this was the phosphorus match, the match with which we are so familiar. according the paragraph what was the benefit of the new phosphorus match? it burst into flame when rubbed on sandpaper. it was made by mixing chemicals. it could be ignited on any dry surface. it threw fire in all directions.

answer - matches required natural chemicals