某工程双代号网络计划如下图所示，其关键线路有（）条。
A．1
B．2
C．3
D．4
参考答案：C
It is both _______ and _______ friendly to cycle to school.[ ]
A. enjoyable, environment
B. enjoy, environment
C. enjoyable, environmental
D. enjoyable, environmentally
国家海洋经济权益维护的主要领域
