A:作∠AOB,使∠AOB=3∠α
B:以点O为圆心作弧
C:以点A为圆心,线段a的长为半径作弧
D:作∠ABC,使∠ABC=∠α+∠β
甘蓝与白菜均为二倍体(2N),“白菜﹣甘蓝”幼苗培植过程中杂种细胞内最多含有____ 个染色体组.
下列等式从左边到右边的变形属于分解因式的是( )
(____) These are all books about science.
(____) That's a good idea.
(____) Let's put them on this shelf.
(____) We can put them on Shelf B.
(____) Let's make a home library.
下列公式都符合a= bc 的形式,能说a与b成正比,a与c成反比的是( )