题目

根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。 A. Although it is demanding B. Whichever type is desired C. However, an academic program is not required D. For volunteer firefighters the procedure is similar E. But joining a volunteer fire department is totally different F. Training consists of classroom work and practical training G. Also, a candidate must be able to respond quickly in emergencies There are several differenttypes of fire departments. Some hire full-time paid firefighters and some ar方差s2=1n[(x1-.x)2+(x2-.x)2+…+(xn-.x)2]，其中n表示数据的个数数据的个数，.x表示平均数平均数，s2表示方差方差，标准差是方差的算术平方根．