钢在熔化成钢水的过程中( )
A:吸热,温度升高
B:吸热,温度不变
C:放热,温度降低
D:放热,温度不变
His ________ to become a pilot was held back by his poor eyesight.
小麦和青蛙个体发育的起点都是( )
根据汉语提示完成句子