Direction: Correct passive form of the following sentence:
'Orange tastes sour' is:

The given sentence 'Orange tastes sour' belongs to a category of verbs called quasi-passive or middle voice verbs (verbs that are active in form but passive in meaning).
The standard rule for converting a quasi-passive sentence containing a sensory adjective into the passive voice is:

$$\text{Subject}+\text{helping verb}+\text{adjective}+\text{when}+\text{past participle of main verb}$$

Following this rule, the voice conversion yields: Orange is sour when tasted.