Related to the Economics in Practice on Page 51: the Amazon

Related to the Economics in Practice on page 51: The Amazon Kindle and the electronic textbooks available for the Kindle are complementary goods. Electronic textbooks and traditional, hard copy textbooks are substitute products. If the price of traditional, hard-copy textbooks increases,

A) demand for traditional, hard-copy textbooks decreases and demand for electronic textbooks increases.
B) the quantity of traditional, hard-copy textbooks demanded decreases and demand for electronic textbooks increases.
C) the quantity of electronic textbooks demanded increases and demand for the Kindle increases.
D) the quantity of electronic textbooks demanded increases and demand for traditional, hard-copy textbooks decreases.