Answer:
The concentration of DDT in-ring seals is higher than the concentration in the arctic cod because the concentration of DDT increases in the higher food chain due to biomagnification.
When organisms at lower food chain bioaccumulate chemicals like DDT get eaten by organisms at higher food chain then the concentration of DDT increases called biomagnification.
Arctic cod are the small fish which eats small copepods, then arctic cod is eaten by big fish and then these big fishes are eaten by ring seals. Therefore ring seals have a higher concentration of DDT than arctic cods.
Flow chart of biomagnification :
Tiny algae→copepod→arctic cod→bigger char fish→ring seals