Answer:
(ii) usual care or whole-body cooling
Explanation:
In an experiment there are several types of variables that interact with each other to establish a possible result for a research being done. An example of this are variables called explanatory, which can also be called independent. This type of variable does not influence the other variables and determines what will be the result of the research through this influence. In the case set out in the question above, we can see that the usual care or full-body refrigeration of babies is what will determine the research outcome, so we can conclude that "usual care or full-body refrigeration" is the explanatory variable.