Which of the following does not contain a bound morpheme?

The answer is based on the understanding of morphemes, which are the smallest units of meaning in a language. A bound morpheme is a type of morpheme that cannot stand alone as a word and must be attached to another morpheme to convey meaning.

In the case of the word "orange," it is a free morpheme because it can stand alone as a complete word and convey a clear meaning without the need for any additional morphemes. Therefore, it does not contain any bound morphemes.

In contrast, the other options include bound morphemes. For instance, "dogs" contains the bound plural morpheme '-s,' while "unhappiness" includes both the bound prefix 'un-' and the bound suffix '-ness.' The word "jumping" contains the bound suffix '-ing.' Each of these examples demonstrates the presence of morphemes that cannot function independently.

Thus, the choice of "orange" as the option that does not contain a bound morpheme is correct because it is a free morpheme that stands alone.