Final answer:
The adjective 'black' should be placed directly after the noun 'car' in the sentence 'my friend has a black car.'
Step-by-step explanation:
The correct placement of the adjective in the sentence 'my friend has a black car' is option 4) car poss-my friend black. In this option, the adjective 'black' directly follows the noun 'car', which is the correct placement.