食物中所含的六类营养物质中,能为人提供能量的一组是( )
A:水、无机盐、维生素
B:糖类、脂类、蛋白质
C:糖类、脂类、维生素
D:糖类、脂类、无机盐
____ (judge) from his ____ (excite) news, his friends have found the key to ____ (solve) the problem.
已知平面向量a→=(3,1),b→=(x,﹣3),且a→⊥b→,则x=( )