In an experiment, two different types of recorded music were played

In an experiment, two different types of recorded music were played for neonates in adjacent nurseries in a hospital. In nursery A, classical music was played: in nursery B, rock music was played. After two weeks, it was found that the babies in nursery A cried less, suffered fewer minor ailments, and gained more weight than did the babies in nursery B.

In evaluating the validity of the conclusion suggested by the experiment above it would be most important to know which of the following?
A) The musical preferences of the parents of the two groups of newborns.
Doens't explain the differences of the kids
B) Whether the newborns in both the nurseries were equally healthy and happy at the start of the experiment.
This is the correct option. All things equal, is the music the only change that brought these changes in the neonates.
C) Whether loud rock music can damage the hearing of newborns.
Doesnt explain about the crying,ailments,weight
D) what the average weight of the neonates was before and after the experiment
doesnt really explain this very well as the avg weight gain might be same for a 2 week prrioed always between both nurseries
E) Whether the music was played in the nurseries at all times or only at certain times.
Doesnt explain the issue as the babies could have those tendencies before only.



Please explain in detail the options you choose.