Close your eyes and picture the city of Paris．Now imagine the city without its most famous landmark：the Eiffel Tower．
The unthinkable almost happened．
When French engineer Gustave Eiffel built this tower for the Paris World’s Fair of 1889，it was controversial．The iron structure contrasted(对比)sharply with the historic stone buildings of Paris．Eiffel’s four-legged iron archway was supposed to last only 20 years．That’s when Eiffel’s permit to operate the building would expire(过期)and the city could choose to tear it down．
Yet from the beginning．Eiffel had a strategy to save his building．If the Tower was linked  to important research，he reasoned，no one would dare to take it down．So he would make it a  grand laboratory for science．
Scientific research began just one day after the Tower opened to the public on May 6，1889．Eiffel installed a weather station on the Tower’s third(and highest)floor．He connected  instruments by wire to the French weather bureau in Paris．With these，he measured wind speed  and air pressure．
In 1903，still worried that his building might be torn down，Eiffel got a clever idea．He  asked the French military to conduct its own research on radio communications at the Tower．He even paid the army’s costs．
French army captain Gustave Ferrié worked from a little wooden house at the base of the  Tower's southern pillar．From there，he made radio contact with forts around Paris．Convinced of the importance of radio communications，the army set up a permanent radio station at the  Tower．In 1910，the city of Paris renewed the structure’s permit for another 70 years．
This year marks the iconic structure’s 125th birthday．Over the years，research conducted  there has brought dramatic and unexpected payoffs．During World War I，for instance，the French army used the Tower as a giant ear to receive radio messages．It even led to the arrest of one of the war's most famous spies．
What does the author mean by“The unthinkable almost happened”?

A．The Eiffel Tower was almost torn down．

B．Gustave Eiffel was more than an engineer．

C．It took great efforts to build the Eiffel Tower．

D．The Eiffel Tower has served important purposes．

The Eiffel Tower was controversial because_____________．

A．it was giant and ugly

B．it would expire too soon

C．some historic buildings had to be removed

D．it didn’t match the historic buildings of Paris

How did Gustave Eiffel save the Eiffel Tower?

A．By asking the army to defend it．

B．By showing its importance for tourism．

C．By making it a base for scientific research．

D．By asking the government to renew its permit．

The arrest of a famous spy is mentioned to show．

A．the Eiffel Tower has lost its initial value

B．the Eiffel Tower has existed long enough

C．research done in the Eiffel Tower had unexpected payoffs

D．the Eiffel Tower was successfully preserved during the war