如图所示果实的形成示意图,图中①与④分别代表( )
A:受精卵、胚
B:胚乳、果皮
C:子房、果皮
D:子房、种子
The old town has narrow streets and small houses _______ are built close to each other.
曲线f(x)=x2+3x在点A(2,10)处的切线的斜率为____.