Q14 Question 1 30 in text Recall that the National Bridge Inventory NBI is a database maintained by the Federal Highway Administration FHWA Th database contains the NBI is available at the FHWA Web site www fhwa dot gov Using the FHWA inspection information on the structural integrity of highway bridges An analysis of the data from ratings categorized as structurally deficient functionally obsolete or safe About 13 5 of the bridges were found to be structurally deficient while 3 5 were functionally obsolete What is the variable of interest to the researchers 1 pt a NBI data b Highway bridges c Inspection Rating d United States