题目

Melissa Poe was 9 years old when she began a campaign for a cleaner environment by writing a letter to the then President Bush. Through her on efforts, her letter was reproduced on over 250 donated billboards (广告牌)across the country. The response to her request for help was so huge that Poe established Kids For A Cleaner Environment (Kids F.A.C.E.) in 1989. There are now 300,000 members of Kids F.A.C.E. worldwide and it is the world’s largest youth environmental organization. Poe has also asked the National Park Service to carry out a “Children’s Forest” project in every nation已知函数在时有极大值，则的一个可能值是A． B． C． D．