What is the organ that serves as the starting point of the respiratory system?

The organ that serves as the starting point of the respiratory system would be the nose.  It is where respiration starts by taking in the air from the atmosphere and it also ends here by breathing out carbon dioxide a waste gas produced from the processes in the body which is not utilized by our body.

Nimbostratus is the correct answer.
explanation: nimbostratus clouds are the type of clouds that are mostly likely present on gray, rainy day. these clouds produce continuous rain, snow and there is no thundering or lightening either.