下列物质的转变,不能一步实现的是( )
A:KCl → KNO3
B:Fe(NO3)2 →AgNO3
C:SO3→ Na2SO4
D:H2→Cu
Mary got an ______ from Lisa the day before yesterday. Lisa ______ her to go to her birthday party.
设△ABC的内角A、B、C所对的边分别为a,b,c,且满足cosA2=255,AB→·AC→=3
(1)求△ABC的面积;
(2)求a的最小值.
“癌症算得了什么,再大的困难,我也能克服。我要勇敢地站起来。”这是身患癌症的女孩张仲培在日记中写下的话。这段话告诉我们( )