题目内容：

On June 15th，2012，millions of people watched as 33­year­old Nik Wallenda walked across one of the world's greatest waterfalls on a tightrope(钢丝)．What made the 25－minute walk that was televised live and watched by over 13 million people worldwide even more amazing，is that it was done over the Niagara Falls－An action that had never been attempted before.

Even though Nik was wearing a harness(保护带)，a safety measure provided by ABC，the television network that broadcast the event，his action to keep his balance against the strong winds made for some heart－stopping(令人担忧的) moments for the audience.

Nik，however，never slowed down for even one moment.Wearing special shoes made by his mother，he remained totally focused on the job at hand.It was only when he got to the last stretch near Canada's Table Rock that he knelt down on one knee and finally broke into a smile.Waving and blowing kisses to the cheering audience，he knew he had accomplished a great task，which most people had thought impossible.

While he described the whole experience as peaceful and relaxing，Nik said his biggest challenges came from a totally unexpected source－his 40 pound balancing pole.The balancing pole was so heavy that he could hardly carry it on the tightrope.

One would think that now that Nik has realized his lifelong dream he would be ready to hang up his “balancing pole”．However，the adventurer who already has seven Guinness World Records under his belt，is just getting started－Next up? A 5，000－foot tightrope walk across the Grand Canyon.While the one across the Niagara Falls took years of planning because he had to convince the US and Canadian officials，this one should happen in the very near future.That's because，the Florida resident has already been granted(授予) a permit by the Canyon officials.

1.Why did so many people fix their attention on the event?

A．Because it was done by Nik Wallenda.

B．Because nobody had done it there before.

C．Because it was broadcast live by ABC.

D．Because it was impossible to do the event.

2.What made the audience hold their breath during Nik's performance?

A．How Nik managed to cross the Niagara Falls with safety measure.

B．What Nik would do when he lost his balance on the tightrope.

C．How Nik kept his balance against the strong winds.

D．How long Nik will take to finish the event.

3.What was the greatest difficulty for him to face in Nik view?

A．The supplied tightrope.

B．The safety belt.

C．The balancing pole.

D．The audience's noise.

4.What does the last paragraph mainly talk about?

A．Nik will go on with his dream.

B．Nik's life dream is changing.

C．Permission of governments is important.

D．The Grand Canyon is a dream for Nik.