问题详情

Two major problems for museums are that they have too many visitors and they__________．
A．have higher demands of museums
B．are open to move people with different social background
C．to lengthen their opening hours
D．charge too little for admission
E．have been built and open to public
F．by lowing the admission fees 请帮忙给出正确答案和分析，谢谢！