If an individual buys only two goods and these must be used in a fixed relationship with one another (e.g., coffee and cream for a coffee drinker who never varies the amount of cream used in each cup), then

a) there is no substitution effect from a change in the price of coffee

b) there is no income effect from a change in the price of coffee

c) coffee and cream must be Giffen goods

d) an increase in income will not affect cream purchases