①NaHCO3 ②Al2O3 ③Al(OH)3 ④Al ⑤Na2CO3( )
A:①③④
B:②③④⑤
C:①②③④
D:全部
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一 Do you know Yao Ming?
一 Yes, he is famous playing basketball and a basketball star·
若向量a→=(1,1),b→=(2,5),c→=(3,x).
(1)若b→∥c→,求x的值;
(2)若(8a→﹣b→)•c→=30,求x的值.