Which of the following would be a good way to ensure toddlers are able to nap during the day?
allow for plenty of fresh air and exercise.
b. enlist the of parents, who can wake toddlers an hour earlier than usual.
c. allow children to become sufficiently tired, which is often characterized by irritability.
d. keep them subdued from arrival until after lunch.

I believe is the answer is:

Allow the child to have fresh air and exercise to tire itself out, and also, fresh air is good for everyone.

look at my explanation to why I believe that,

Explanation:

Some regions in the world practice putting there kids down for a nap outside and there are studies which indicate its benefits at helping toddlers/infants to sleep better and longer, although not everyone agrees conclusively on this.

fluid balance is an aspect of the homeostasis of organisms in which the amount of water in the organism needs to be controlled, via osmoregulation and behavior, such that the concentrations of electrolytes (salts in solution) in the various body fluids are kept within healthy ranges. the core principle of fluid balance is that the amount of water lost from the body must equal the amount of water taken in.