When studying abroad last year, Blake found that his U.S. dollars did not stretch as far as he had hoped. Each time he exchanged U.S. dollars for euros, he gave up more U.S. dollars in exchange for less euros. The exchange rate indicates:________.
a. the dollar has gained strength against the euro.
b. the euro is weak against the U.S. dollar.
c. the euro has gained strength against the dollar.
d. the demand for dollars is stronger than the demand for euros.