Use the following list of factors that are related to the aggregate demand curve to answer the next question.
1) rea-balances effect
2) household expectations
3) interest-rate effect
4) personal income tax rates
5) profit expectations
6) national income abroad
7) government spending
8) foreign purchases effect
9) exchange rates
10) degree of excess capacity
which of the above factors best explain the downward slope of aggregate demand curve?

a) 7.9, and 10
b) 4.6, and 7
c) 1, 3, and 8
d) 2, 4, and 6