The phrase 'increase in quantity demanded' signifies:
Hint: look up the terminology associated with movements along and shifts of the demand curve!
a. a movement along the demand curve from left to right (i . e . moving down the demand curve) .
b. a shift of the demand curve to the left.
c. a movement along the demand curve from right to left (i . e . moving up the demand curve) .
d. a shift of the demand curve to the right