Ans. is 'b' i.e., Pulmonary angiography o The definitive diagnostic for pulmonary thromboembolism is pulmonary angiography.o It is the most specific investigation for pulmonary> thromboembolism but it is expensive time consuming and invasive,o Therefore chest CT with contrast has virtually replaced angiography as the diagnostic test.o Best investigation when there is clinical suspicion of pulmonary embolism - Contrast enhanced CT.