Jenny's Chinese _______ a lot since she _______ to China two years ago.
A:improved; came
B:has improved; has come
C:improved; has come
D:has improved; came
把一个苹果(ρ苹果<ρ水)轻轻放入装满水的杯中,苹果静止时将处于____;假设苹果密度均匀,那么将苹果切成大小两块放入水中,大块将____(两空均选填“漂浮”、“悬浮”或“沉底”).
“小白兔,白又白,两只耳朵竖起来,爱吃萝卜爱吃菜,蹦蹦跳跳真可爱.”在兔年唱起这首童谣,仿佛又回到了快乐的童年时光.
抛物线y=ax2+bx+c的图角如图,则下列结论:①abc>0;②a+b+c=2;③a>12;④b<1.其中正确的结论是( )