Which gas is characterized by a sharp and intensively irritating odor?

The gas characterized by a sharp and intensively irritating odor is ammonia. Ammonia has a distinct, pungent smell that can be easily recognized, making it one of the gases most noted for its strong odor. This attribute is due to its molecular structure, which interacts with sensory receptors in the nasal passages, causing strong irritation, especially in high concentrations.

The irritative effect of ammonia is significant, as it can cause discomfort when inhaled, leading to coughing and throat irritation. This gas is commonly used in household cleaning products and is also a byproduct of various industrial processes.

The other gases listed do not exhibit the same level of irritation or recognizable odor. Hydrogen is colorless and odorless; chlorine has a strong smell, but it is different from ammonia's specific irritating effect; nitrogen is also colorless and odorless. Therefore, ammonia is the correct answer due to its sharp, intensively irritating odor.