Directions: Read the following passages and choose the best answer for each question. (Item 1-9)
    The idea that spaceships may someday trek from star to star makes great science fiction but bad science. The laws of physics and the properties of matter limit this speed of spaceships, making it impossible to travel between stars in any reasonable time.
    This is a surprisingly unpopular message. Instead of being relieved that we can’t be invaded by hostile aliens, people are disturbed by the idea that our technology is approaching some theoretical limit so soon after it first stated. Only 160 years separate the first steam locomotive from manned space flight, a stupendous rate of progress. Surely if technology could take us from 3 miles per hour to 25,000 miles per hour (7 miles per second) in only 160 years, someday speeds in excess of 186 miles per second should be possible.
    Unfortunately, technology doesn’t work this way. Human experience shows us that new technologies reach their practical limits early in their development. The Great Pyramid of Egypt was built about 260 B.C., only a few hundred years after the Egyptians first learned to cut and move large blocks of stone. They continued building pyramids for another 1,000 years, but never again one as big.
    Men landed on the moon only eight years after Yuri Gagarin’s first orbital flight. The moon landing may be our Great Pyramid, an accomplishment never again to be equaled. Although a manned mission to Mars may be technologically possible, it’s questionable whether it is justified in terms of its costs and risks. Even if peace and democracy should reign throughout the world and $1 trillion a year in armament expense is no longer needed, there will be many other things to do with the money.

The main idea of the passage is that