What is difference between primary and standard solution?

A standard solution is solution that is a containing a precisely known concentration of an an element. Primary  it's typically a reagent which can ve weighed very easily, and which is so pure that the weight of it is truly representative of the number of molecules that it contained 

I’d have to say no because without oxygen in the water the fish would all be dead. so if you want to fish for dead fish, pick the ponds with the lowest oxygen concentrations.

The process is c.convection