钩虫卵的形态特点是
A．卵壳与卵细胞间有明显的间隙B．椭圆形C．排出不久的卵内含2～8个卵细胞D．无色透明E．以上都是
参考答案：E
— I wonder if you can go shopping with me together.
— Sorry. I _____ a letter all the morning and haven't finished it yet. [ ]
A. am writing
B. was writing
C. have written
D. have been writing
一根铁丝长48米，我想用它围成正方形。围成的正方形的面积是多少？
