The correct choice is (b) It is a weak oxidizing agent
For explanation: Nitric acid is a very weak reducing agent since it has a polar O – H bond. This breaks to donate the H^+ ion which is why it is a strong oxidizing agent and a strong acid. Since there is only one cleavable O – H bond, the basicity of nitric acid is unity (one HNO3 molecule can donate only 1 H^+ ion). It exists as a planar molecule in vapor phase.