When the price of a good decreases, how do the income effect and the substitution effect change the quantity demanded of the good?
选项：

A:Both the income effect and the substitution effect increase the quantityDemanded.
B:The income effect increases the quantity consumed, but the substitution effectMay increase or decrease the quantity demanded.
C:The substitution effect increases the quantity demanded, but the income effecMay increase or decrease the quantity demanded.