This diploma ( 毕业文凭 ) ________ that you have completed high school.

龚自珍诗 "昨日相逢刘礼部，高言大居快无加。从此烧尽虫鱼书，甘作东京卖饼家。 "反映了他的学术转向 ()

设 f(0)=0 ,则 f(x) 在 x =0 处可导の充要条件为（）

We regret to ________ that it may not be possible to deal with every request.

用和平赎买的方法对 _________进行改造。