补全短文
a professional career amateur performers admiring fans free of charge A. not only 【T13】______, but professional artists as well B. to make contact with their 【T14】______ C. they rent out space to performers 【T15】______ D. before beginning 【T16】______ Some of the most popular attractions across America are the many free concerts offered to the public throughout the year. These involve 【T17】______. The public parks of many cities across the country usually have bandstands and large lawns. As a service to citizens, 【T18】______. Amateur groups, with nothing more than a desire to perform, offer their talents freely to the public. Semi-professional artists are pleased to get the chance to perform before the public to perfect their craft and nurture the hope of being discovered 【T19】______. Famous professionals also give free concerts 【T20】______. Often such concerts are sponsored by a large corporate organization and offered to the public free of charge as a cultural service and support for the arts.