The level of measurement which is qualitative is nominal.
It is the only level of measurement which is only qualitative, whereas ordinal can be either qualitative or quantitative (depending on data), and interval and ratio can only be quantitative.
The term qualitative refers to the fact that non-numerical entries are used, meaning there are no numbers, and the word nominal refers to the Latin word for nouns, or words, which is why that is the correct answer. The rest of the options use numbers, but nominal doesn't.