What is full form of CBSE:

Central Board of Secondary Education
Center Board of Second Education

What is full form of ICSE:

Indian Certificate of Secondary Education
International Certificate of Second Education

What is full form of IGCSE:

International General Certificate of Secondary Education
Intermediate General Certificate of Second Education

What is full form of NIOS:

National Institute of Open Schooling
Nation Institute of Open School

What is full form of IB:

International Baccalaureate
Intern Bachelor