Consider the following statements with respect to the Tropical Cyclones:

a. A mature tropical cyclone is characterized by the strong spirally circulating wind around the centre, called the eye.

b. Around the eye is the eyewall, where there is a strong spiralling ascent of air to a greater height reaching the tropopause.

c. The wind has the minimum velocity in the eyewall region.

Which of the statements given above are correct?