The correct option is B is being repaired
The events mentioned in the given sentence take place at the moment the speaker speaks. The line "I am taking a taxi" suggests the same.
'Am taking' is in the present continuous tense. The blank, too, indicates a continuous action during the present moment. Hence the tense of the verb to be filled will also be in the present continuous tense.
Option B: 'Is being repaired' is in the present continuous tense. Hence it's the most suitable option.
(Also, the verb 'is being repaired' is passive, because the subject 'car' is receiving, and not performing the action 'repaired'.)
Hence option B is correct.
Option A: 'Was been repaired' is grammatically incorrect. 'Been' suggests a perfect tense whereas 'was' suggests a continuous tense.
Option C: 'Was repaired' is in the simple past tense, but the action is taking place in the present, as explained above.
Option D: Similarly, 'had been repaired' is in the past perfect tense. So, options C and D are incorrect.