题目

完形填空Around13000 years ago North America had a wider variety of mammals (哺乳动物) than modem Africa. There were multiple horse species，camels and some now-extinct animals. And such1creatureswere not just found in North America. On every continent mammals on averagewere a lot larger from around 2.5 million until about 11700 years ago.Scientistshave long debated what caused all these large creatures to go extinct whilemany of the smaller ones2.A team of researchers led by biologistFelisa Smith analyzed evidence from millions of years' worth of mammalianextinctions and found that on—Excuse me, sir_____ is Blue Sky Supermarket?       —About 20 minutes` walk. [     ]A. How many timesB. How farC. How long