为探究声音的反射与吸收特点，小明同学进行了实验探究。

$\frac{9}{18}\text{=}\frac{1}{\left(\right)}$

$\frac{13}{91}\text{=}\frac{1}{\left(\right)}$

15．－Tom, you've got an A in the final English exam. Congratulations!
－Thanks. But I never thought the result would come out so fast. The papers_____when I left the teacher's office just now.

Please give a banana to me. (改同义句)

 Please give ____ ____ ____.

如图，在正方形ABCD中，E，F分别为AD，CD的中点，BF与CE相交于点H，直线EN交CB的延长线于点N，作CM⊥EN于点M，交BF于点G，且CM=CD，有以下结论：①BF⊥CE；②ED=EM；③tan∠ENC= $\frac{4}{3}$ ；④S_{四边形DEHF}=4S_△CHF，其中正确结论的个数为（   ）