_______ for several weeks, the city was short of food and clothing.

A．As having flooded

B．As flooding

C．Having been flooded

D．To flood

设f（x）为定义在R上的奇函数，当x≥0时，f（x）=2^x+2x+b（b为常数），则f（-1）=（　　）

A．-3

B．-1

C．1

D．3