Why manganese and Magnesium are good reducing agents and not the other metalsas other metals cannot liberate hydrogen gas when treated with nitric acid

Hiii 

Nitric acis is strong oxidising agent as soon as hydrogen gas is formed in the reaction it gets oxidised into H2o by nitric acid and itself reduced to No2 N2O or NO , hydrogen gas isnot evolved.

nitric acid is a good reducing agent so’hydrogen gas is formed in the reaction gets oxidised itself into water by nitric acid and itself reduced to N2O NO NO2 HYDROEN GAS IS NOT EVOLVED