TNT cable channel began using the slogan $"$TNT knows drama" in early $2002.$ It wants to determine how its viewership has changed since it has changed its programming focus. It has decided to use secondary data to determine if its viewers' demographics have changed. A potential disadvantage of this research plan is:

Select one:

a$.$ the difficulty of holding certain variables constant while varying one factor of interest

b$.$ the high cost of collecting secondary data

c$.$ the length of time it takes to collect secondary data

d$.$ interviewer bias during the collection process

e$.$ the information not fitting the needs of the research problem