软件工程方法的产生源于软件危机，下列哪个是产生软件危机的内在原 　　Ⅰ．软件的复杂性　　Ⅱ．软件维护困难　　Ⅲ.软件成本太高　　　Ⅳ软件质量难保证

A．Ⅰ

B．Ⅱ

C．Ⅰ和Ⅳ

D．Ⅲ和Ⅳ

The place was flooded ________ it had been raining for several weeks.[ ]

A. because

B. because of

C. ever since

D. as a result of