If a country places a 10 percent tariff on imports of shoes and a 5 percent tariff on imports of all materials required for making shoes, the effective rate of protection provided for the shoemaking industry will be
选项：

A: higher than 10 percent.;
B:10 percent. ;
C:5 percent. ;
D:between 10 percent and 5 percent, depending on the importance of imported materials.