鸟类的生殖特点是
①体内受精 ②受精卵大，含养料多 ③卵外有坚硬的卵壳保护 ④ 亲鸟哺育幼鸟 [ ]
A．①②
B．③④
C．②③④
D．①②③④
答案：D
下图“褶曲剖面图”中岩层的新老关系为
A．自西向东由老到新
B．自东向西由老到新
C．自中心向两侧由老到新
D．自中心向两侧由新到老
________with what the students had done, the teacher praised them highly. [ ]
A. Delight
B. Delighting
C. Delighted
D. Being delighting
