In the inner ear, a coiled tube called the contains the receptor cells for hearing.
a. basilar
b. cochlea
c. pinna
d. ossicle

The correct answer for the blank is- b. cochlea.

The cochlea is a fluid filled, coiled like sense organ that is located in the inner  ear and functions to translate the vibrations of sound/ sound waves coming from outside into signals ( called nerve impulses). It possesses tiny hair cells that act like sensory receptors to pick up the sound waves.

The nerve impulses are sent to brain via auditory canal, where they are processed and perceived as sound, which is then understood by the person.

Thus, option B) is the right answer.