单项选择题

What is the author's main concern

A．How to render automobiles pollution-free.
B．How to make smaller and safer automobiles.
C．How to solve the problem of traffic jams.
D．How to develop an automated subway system.

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热门试题

单项选择题

What provides autos with electric power in an automated highway system

A．A rail.
B．An engine.
C．A retractable arm.
D．A computer controller.

单项选择题

One significant improvement in the future car will probably be ______.

A．its power source
B．its driving system
C．its monitoring system
D．its seating capacity