67.
According to the researchers, teenage
mothers tend to have less bright children because .
A. they aren’t so good at childcare
B. they usually have less fat than mature
women
C. they aren’t physically strong enough
D. their waist and hip measurements differ
less
D
United States President George W. Bush is
expected to issue a directive in the next few weeks. It will give the US Air
Force a green light for the development of space weapons, US media reported
last week.
This would potentially start a new global
arms race, some experts have warned.
To keep that from happening, last Wednesday
the White House explained that it was not considering putting weapons in space.
It said it was making a shift in US space policy to allow for
protection of satellites.
But some defense analysts and arms control
advocates argue that the policy will pave the way for the US to put both
defensive and offensive( 攻击性的)weapons in space.
“No one should be fooled,” said Theresa
Hitchens, an American weapons expert.
The US is now restricted by a 1996
directive signed by President Bill Clinton. Plans for space weapons were
vetoed( 否决)by the Clinton
cabinet. The directive emphasized the peaceful use of space , in agreement with
almost unanimous(一致的 )global opinion.
The US military has placed importance
on space and has sent up numerous satellites for troop communications and to
provide intelligence and data to guide bombs to their targets.
The US Air Force wants to develop space-
based weapons that could strike targets anywhere in the world within 90 minutes
of receiving the order to open fire.
These new weapons under development cover a
wide range. They include hunter- killer satellites and orbiting weapons. And
they use lasers, radio waves, or even dense metal tubes, known as “Rods from
God”, dropped from space to do the damage.
There are many barriers to the setting up of
this kind of program, experts say.
First is the coast. It is estimated that the
budget may be US $220 billion to US $ 1 trillion( 万亿).
The technical difficulties of developing
reliable space weapons are also a problem.
And, the program will draw strong criticism
from around the world. Experts worry about starting a space arms race.
