Right option is (a) Hyponitric acid
Best explanation: Hyponitric acid does not exist. The rest three mentioned are commonly occurring oxoacids of nitrogen. Hyponitrous acid, H2N2O2 is an isomer tautomer of nitramide, with the structure of the former being HON = NOH. Nitrous acid, HNO2 is usually formed in the atmosphere prior conversion to nitric acid. It is highly unstable.