What cumulative dose of Bleomycin is linked to pulmonary toxicity?

Bleomycin is known to cause pulmonary toxicity, with the risk increasing with higher cumulative doses. The cumulative dose threshold at which the risk of pulmonary toxicity significantly increases is typically considered to be around 400 units. Therefore, option D (400 units) is the correct answer.

Options A, B, and C (100 units, 200 units, and 300 units) are lower cumulative doses that are less likely to result in significant pulmonary toxicity compared to 400 units.