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平常人们常说：“未见其人，先闻其声”，就是根据各人的______不同分辨出是谁的声音的．用力敲锣，锣面振动的______就大，锣声就响，这表明：响度的大小与发声物体的______有关．

答案

不同的人发声的音色不同；用力敲听到声音响度大，观察到振动幅度大，所以响度和振幅有关，振幅越大，响度就越大．

故答案为：音色；振幅；振幅．

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I am honored to be here today, (1) Harvard at this celebration of the College Board’s half century of working to promote (2) and equal opportunity in higher education.
Before I say anything else, I want to thank everyone in the room for the work you do every day to make college (3) , available, and (4) for millions of young people across the country.
I want to focus my remarks on a matter of (5) to American familiesand to the future of the nation -- restoring education to its proper role as a (6) to equal opportunity and (7) in our society.
This has been an (8) in higher education, with great and creative efforts made by many institutions. Earlier this year, we announced a new (9) at Harvard aimed at the students from families of low and (10) income. Under our new program, families with incomes of (11) will no longer be expected to contribute to the cost of attending Harvard for their children. Families with incomes of less than $ 60,000 will also see their (12) reduced.
We are proud of this effort at Harvard, but we are aware that the programs of individual institutions with means can never be a substitute for our shared (13) to provide adequate funding for Pell grants and other financial aid, and for the state and community college systems that make higher education (14) and affordable for the (15) .
There is something empty about (16) initiatives that may be right for one institution without attention to their broader impact. (17) , we (18) if we urge changes in national policy without doing what we can on our own campuses.
In this spirit, I want to (19) today a problem that is emerging with (20) in this nation.
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单项选择题

所谓加热炉的大小，是用什么指标来决定的？（）

A、炉管的直径和长度

B、被加热介质的流量

C、炉膛的大小

D、总热负荷的大小
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