The correct answer is: No vehicles are allowed to park here.
The verb “to allow” means to give permission for something to happen. In this case, the speaker is saying that no vehicles are allowed to park in the area. This means that no one has permission to park there, and anyone who does so will be breaking the law.
The other options are incorrect because they do not accurately reflect the meaning of the sentence. Option A, “is allowed,” is in the present tense, but the sentence is about a general rule that is always in effect. Option B, “has been allowed,” is in the past tense, but the sentence is about a current rule. Option C, “is being allowed,” is in the present progressive tense, but the sentence is about a general rule that is not specific to any particular time.
In conclusion, the correct answer is: No vehicles are allowed to park here.