I'm considering______a teacher after graduation because a teacher is often considered______the engineer of human souls.
A:to become;to be
B:to become;being
C:becoming;being
D:becoming;to be
能预测一个国家未来人口数量动态变化的最关键种群数量特征是____ .
如图,BD,CE分别是△ABC的高,且BE=CD,求证:Rt△BEC≌Rt△CDB.
导致唐朝由盛转衰的历史事件是( )