According to the passage, in the period prior to 1975, each of the following consideration
A.the number of clerical workers in that group
B.the number of women among the clerical workers in that group
C.whether the clerical workers in that area were concentrated in one workplace or scattered over several workplaces
D.the degree to which the clerical workers in that group were interested in unionization
E.whether all the other workers in the same jurisdiction as that group of clerical workers were unionized