A:I realized
B:did I realize
C:I had realized
D:had I realized
“春蚕到死丝方尽”,茧是家蚕完全变态发育中的( )。
计算:3x+2x=( )
比较大小
12×3____35 33×2____34×2
23×2____32×2 12×2____22×1
合理膳食是指( )