① —Who is she?
—She's my teacher,Miss Fang.
②—Who is she?
—She's my teacher,Mrs Wang.
③—Who is he?
—He's my teacher,Mr Zhang.
④—Who is he?
—He's my teacher,Mr Liu.
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俗话说:“井无压力不出油,人无压力轻飘飘”。对这句话理解正确的是( )
关于原子核的结合能,下列说法正确的是( )