The correct answer is D. Food packets are being distributed to the flood victims by the authorities.
The sentence is in the present continuous tense, which is used to describe actions that are happening now or that are happening repeatedly. In this case, the authorities are currently distributing food packets to the flood victims.
Option A is incorrect because it uses the simple past tense, which is used to describe actions that happened at a specific time in the past. In this case, the authorities did not distribute food packets to the flood victims at a specific time in the past.
Option B is incorrect because it uses the singular verb “is” with the plural subject “food packets.” The subject and verb must agree in number, so the correct verb should be “are.”
Option C is incorrect because it uses the past progressive tense, which is used to describe actions that were happening at a specific time in the past. In this case, the authorities were not distributing food packets to the flood victims at a specific time in the past.