To many environmentalists, the extinction of plants—accompanied by the increasing genetic uniformity of species of food crops—is the single most serious environmental problem. Something must be done to prevent the loss of wild food plants or no-longer-cultivated food plants. Otherwise, the lack of genetic diversity could allow a significant portion of a major crop to be destroyed overnight. In 1970, for example, southern leaf blight destroyed approximately 20 percent of the United States corn crop, leaving very few varieties of corn unaffected in the areas over which the disease had spread. Which of the following can be inferred from the passage above

A．Susceptibility to certain plant diseases is genetically determined.

B．Eighty percent of the corn grown in the United States is resistant to southern leaf blight.

C．The extinction of wild food plants can in almost every case be traced to destructive plant diseases.

D．Plant breeders focus on developing plants that are resistant to plant disease.

E．(E) Corn is the only food crop threatened by southern leaf blight.

永昌公司2009年10月开业，领受房产证、工商营业执照、商标注册证、土地使用证各一件；同江海公司签订加工承揽合同一份，合同载明由永昌公司提供原材料金额300万元，需支付的加工费为20万元；另订立财产保险合同一份，保险金额为1000万元，支付保险费10万元。已知加工承揽合同的印花税税率为0.5‰，财产保险合同的印花税税率为 1‰，权利许可证照的定额税率为每件5元，则永昌公司应纳印花税为( )。

A．220元
B．240元
C．600元
D．800元