He was dismissed from the service for his insistent _.

Explanation

'Alertness' means "the quality of being alert, vigilant". 'Nobility' means "the quality of being noble in character, virtue". 'Disobedience' means "failure or refusal to obey rules or someone in authority". 'Alliance' means "a relationship based on similarity of interests, nature, or qualities".For one to be dismissed from service, negative characteristics are usually associated with the reason and behaviour. Hence disobedience is the most appropriate option.