On examination a loud P2 is noted associated with a left parasternal heave. An ECG shows evidence of right ventricular strain and a diagnosis of pulmonary hypertension is suspected.. Cardiac catheterization

A 60-year-old man is investigated for progressive shortness of breath. On examination a loud P2 is noted associated with a left parasternal heave. An ECG shows evidence of right ventricular strain and a diagnosis of pulmonary hypertension is suspected.
Which one of the following is the single most important test to confirm the diagnosis?
A.A Echocardiography
B.A High resolution CT thorax
C.A Cardiac catheterization***
D.A Pulmonary angiography
E.A Ventilation perfusion scanning.