Marine Midland Bank sent market researchers door-to-door in the neighborhoods surrounding its branch banks. Each researcher wanted to spend 15 minutes talking with a head of the household about his or her savings accounts to discuss why he or she did not also have checking accounts and credit cards with the bank. Marine Midland researchers were using __________ to collect these data.
A. ethnographic research
B. observational data collection
C. individual interviews
D. intercept interviews
E. secondary interviews