The correct option is D is grown
A sentence in passive voice focuses on the person or thing that receives an action rather than the person/thing that performs the action.
For example, 'My room was cleaned by me.'
The basic structure of passive voice is:
the appropriate form of the verb 'to be' + past participle
Option B: The given sentence states a fact, hence it's in simple present tense. So, the simple present form of 'to be', 'is' is used. (The simple present tense states a general fact or a usual habit.)
'Is grown' is the appropriate structure, formed by the simple present tense verb 'is' + past participle (grown). Hence option B is correct.
Option A: 'Is being' is in present continuous tense. But the sentence does not state a particular action that is being carried out at the moment. Hence A is incorrect.
Option C: 'Grows' is a verb in the active form: Tea grows in gardens.... It changes the thing "tea" to perform, rather than receive, the action. Hence C is incorrect.
Option D: 'Is growing' is not the correct verb form used in the passive voice. 'Growing' is a present participle whereas the required verb form is a past participle. Hence D is incorrect.