The phrase "this relationship"( in Line 3, Para. 5 )refers to the connection between ______and the incidence of heart disease.

A．the high incidence of heart disease in some countries
B．the effect of fish eating on people's health
C．the changes in people's diet
D．the daily fish consumption of people in different cultures

A．Because American people drink too much spirits.
B．Because there are a great number of fat people there.
C．The author doesn't give a definite answer.
D．Because American people eat too much fatty fish.