The function of the first sentence in this passage is to （）

单项选择题It is very difficult to get from one place to another in Tokyo because（）

A．the city is so large and so high
B．there is no traffic
C．we don’t know the road
D．the city is so large and the traffic is so heavy

单项选择题Dinosaur scientists can get information directly by （）

A．studying dinosaur fossils
B．examining modern animals
C．watching dinosaurs
D．using telescopes