Phonetic features relevant in describing vowel sounds include: O a manner of articulation, tongue height, tenseness, place of articulation
tongue height, voicing, place of articulation, tenseness
ОВ.
voicing, place of articulation, manner of articulation
OC. .
op tongue height, tongue advancement, lip rounding, tenseness

The correct answer is A. Phonetic features relevant in describing vowel sounds include manner of articulation, tongue height, tenseness, place of articulation  and voicing.

Explanation:

Phonetic features are the building blocks with which one can describe and distinguish phonemes and language sounds in the languages of the world; such building blocks can be tone, aspiration, nasalization and more.

When pronouncing a specific phoneme, the speech apparatus performs a number of coordinated articulatory movements, which cause a corresponding amount of acoustic phenomena. The tongue is placed in a certain position, as are the vocal folds, the palate is closed or opened, the air flow from the lungs is completely or partially blocked, or not at all and more. These various articulatory movements and the accompanying acoustic properties cannot themselves carry any semantic information; that is, they do not constitute phonemes, but they can distinguish different phonemes.