A:how our city Dawukou looked like
B:what our city Dawukou looked like
C:what did our city Dawukou look like
D:how did our city Dawukou look like
制作面包和酿酒过程中,酵母菌进行的生命活动包括( )
①光合作用 ②呼吸作用 ③消化吸收 ④生长繁殖.
设变量x,y满足约束条件y≥xx+2y≤2x≥-2,则z=x-3y+2的最小值为( )
维生素是一类比较简单的有机物,能为人体提供能量.(判断对错)