—Although my son failed the exam, he tried his best to________
— He is old enough to control his feelings.
A: raise his spirits
B: keep himself angry
C: keep himself down
子代体细胞核中的每一个基因一半来自父方,一半来自母方.(判断对错)
下图所示的微观变化,其基本反应类型是()
抛物线y=-x-12-2的顶点坐标是( )