The correct answer is C. A something in the air, intangible.
Step-by-step explanation
The first characteristic of iambic pentameters is that each verse contains ten syllables, this occurs in option C. "A/ some/thing/ in/ the/ air/, in/tan/gi/ble/". Additionally, the ten syllables form groups of two nouns as an iamb, which is in a stressed syllable followed by a stressed syllable, this pattern can be seen in the verse "A/ some/thing/ in/ the/ air/, in/tan/gi/ble/". This means, there are five iambs (Penta equals five). According to the above, the correct answer is C. A something in the air intangible.