题目内容：
根据下面内容，回答题：At first glance,there hardly seems to be any comparison between Ravenna and Rome,but backin the 5th century ,it was Ravenna that served as capital of the Western Roman Empire． In this city,Roman rulers built monuments which are famous, then and now, for their sweeping mosaics (镶嵌图案)． Seven of Ravenna's eight buildings from the 5th and 6th centuries are spectacularly decoratedwith examples of this ancient art． "In the past, many people couldn't read or write," says tour guideand Ravenna native Silvia Giogoli． "Mosaics were a way to explain the religion and the political situ-ation to the people． " Visitors to Ravenna can look at pieces of art by ancient artists, listen to musicians, and learn to
make their own masterpieces．
Travel Tips
When to Go:June--October; weather is pleasant in April and May but historic sites can getcrowded with school groups．
Where to Stay:Walk through historic district sites from Albergo Cappello and stay at a modernHotel Centrale Byron．
How to Get Around:Take the train from Bologna, and then walk, bike, or use taxis within thecity．
Where to Eat or Drink:Housed in a former movie theater, two-storey Ristorante Cinema Alex-ander blends 1940s Hollywood flavor with homemade Emilia Romagna courses and attentive service(helpful in translating the menu)． For fresh seafood, try Osteria L'Accigua and Da Buco．
What to Buy : Watch the next generation of Emilia Romagna mosaic artists create contemporaryand traditional pieces in local studios where modern artists use the same methods as their Byzantineforefathers．
What to Read Before You Go:Ravenna in Late Antiquity, by Deborah Mauskopf Deliyannis-． 2010) ,provides a wide-ranging look at the city's art, architecture, and history．
In ancient times, mosaics were used to A．display artistic achievements
B．compete with Roman paintings
C．explain religion and politics
D．teach reading and writing
参考答案：
答案解析：