Which data type can show the extent of differences between values but does not have a true zero point?

The correct answer is interval data type. This type of data allows for comparisons of the differences between values. It provides meaningful information about the magnitude of differences; for example, the difference between 10 degrees and 20 degrees is the same interval as between 20 degrees and 30 degrees.

However, interval data does not have a true zero point. A classic example of this is temperature measured in Celsius or Fahrenheit. In these scales, zero does not indicate the absence of temperature; rather, it is just a point on the scale. Therefore, while you can say that one temperature is higher or lower than another and quantify that difference, you cannot say that 0 degrees means there is "no temperature" in the same sense that you can with absolute zero in the Kelvin scale.

Each of the other data types has distinct characteristics that do not align with the question's criteria. Nominal data is categorical without any intrinsic order, ordinal data has a defined order but does not quantify the difference between categories, and ratio data has both a true zero point and meaningful intervals. Thus, interval is the appropriate answer for this question.