下列微粒的符号你会写吗？填填看．

（1）2个氮原子 ______；（2）5个氨气分子 ______；（3）1个硫酸根离子 ______．

Which statement about the preliminary design stage of a software development project is true ______

A．The preliminary design is an internal document used only by programmers

B．The preliminary design is the result of mapping product requirements info software and hardware functions

C．The preliminary design of the product comes from the requirement specification

D．The developers produce the preliminary design by defining the software structure in enough detail to permit coding