According to John P. Caskey, pawnshops are important because

A．they provide great dollar value to the poor

B．they make big loans

C．they are serving the majority of the population

D．they make a, large number of loans to the poor

C类（）：用于参加初级考核的模型没有限制；用于参加中级考核的模型旋翼直径须大于（）毫米（含）；用于参加高级考核的模型旋翼直径须大于（）毫米（含）。