污油与汽油换热，如何安排两流体的流径？为什么？
参考答案：
污油走管内，汽油走管间，便于清洗。
----I am looking for information on social safety.
----You can take this book. Social safety is _______ introduced in it
A．regularly
B．naturally
C．usually
D．specially
现代汽车广泛采用（）发动机。
