The main income of the city of Valencia is from its （）

单项选择题When was Valencia the most important city in Spain（）

A．2nd century
B．8th century
C．13th century
D．20th century

单项选择题What is the main difference between the two parts of the city（）

A．The colour of the buildings
B．The age of the buildings
C．The colour of the roofs
D．The length of the streets