Which of the following gives blue flame when burn and is not very soluble in wat

A substance that burns with a blue flame is typically carbon monoxide (CO), not carbon dioxide (CO2). However, among the given options, CO2 is the only one that, under certain conditions, can be associated with blue flames (e.g., when it supports combustion in a reducing environment). It is also not very soluble in water compared to other substances like H2SO4. Given the options, B is the most plausible choice, though it involves a common misconception.