鸟卵的结构中相当于卵细胞的一组是（　　）

A．卵黄膜、卵黄、胚盘

B．卵壳膜、卵白、卵黄

C．卵壳、卵壳膜、卵白、卵黄

D．整个鸡卵

Which of the following statements is correct

A． The definition phase results in the Software Requirements Specification.

B． Testing is optional in software life cycle.

C． CASE tools can only aid in the design phase of a software life cycle.

D． A change during a later phase does not require the documentation of all earlier phases to be updated.