The correct answer is option 'C', which states that cyber-security threat is not considered or confronted by the National Integration Council. The National Integration Council (NIC) is a government body in India that aims to address and resolve issues related to the integration of diverse communities and regions of the country. It was established in 1961 and consists of representatives from political parties, religious groups, academia, and civil society.

Linguism:
Linguism refers to discrimination or prejudice based on language. In a country as linguistically diverse as India, where multiple languages are spoken, language-based discrimination can be a significant challenge to national integration. The National Integration Council recognizes the importance of addressing linguism and works towards promoting harmony and equality among different linguistic communities.

Casteism:
Casteism is a social issue deeply rooted in the Indian society, where individuals are discriminated against based on their caste. The caste system has been a long-standing challenge to national integration, as it creates social divisions and hinders the progress and unity of the country. The National Integration Council recognizes the importance of eradicating casteism and works towards creating a more inclusive and equal society.

Threat of Regional Violence:
The threat of regional violence refers to conflicts and tensions between different regions or states within the country. Regionalism can sometimes lead to violence and disruption of peace, which poses a challenge to national integration. The National Integration Council aims to address and resolve such regional tensions through dialogue, negotiation, and policy interventions.

Cyber-security Threat:
Cyber-security threats, on the other hand, are not directly related to national integration. While cyber-security is an important issue for the overall security and well-being of the nation, it is not specifically within the purview of the National Integration Council. Cyber-security threats are typically addressed by specialized agencies and departments, such as the Ministry of Home Affairs, Ministry of Electronics and Information Technology, and various law enforcement agencies.

In conclusion, the National Integration Council primarily focuses on addressing issues related to linguism, casteism, and the threat of regional violence. While cyber-security is an important concern, it falls under the domain of specialized agencies and departments rather than the National Integration Council.