Air is approaching a converging–diverging nozzle with a low velocity at 20°C and 300 kPa, and it leaves the nozzle at a supersonic velocity. The velocity of air at the throat of the nozzle is
(a) 290 m/s
(b) 98 m/s
(c) 313 m/s
(d) 343 m/s
(e) 412 m/s