杂交育种所依据的原理是
The movie was ________. I fell asleep half way through it.
未成年人需要摄人足够的钙促进骨骼的生长.下列食物中钙含量最低的是( )
在酿制酒酿的实验中,用冷开水冲冼蒸熟的糯米的目的是( )