Which of the following compounds is characterized as a water-soluble gas with a strong, irritating odor?

The compound characterized as a water-soluble gas with a strong, irritating odor is indeed formaldehyde. Formaldehyde is commonly encountered in funeral service contexts, notably as a preservative and disinfectant in embalming fluids.

When formaldehyde is in gas form, it is known for its pungent and irritating smell, which can be quite offensive to humans, particularly at higher concentrations. Its solubility in water allows it to dissolve readily, leading to its widespread use in aqueous solutions for various applications, including in the preservation of biological tissues.

Ammonia, while also having a strong odor and being water-soluble, is more commonly associated with a different type of irritable scent, more akin to that of urine or decaying matter. Chlorine has a distinct smell as well, but it is not typically classified as water-soluble in the same context of being used in embalming solutions. Carbon dioxide, in contrast, is a colorless, odorless gas that does not possess the irritating odor characteristic of formaldehyde or ammonia.

Hence, formaldehyde stands out due to its strong, irritating odor and its properties as a water-soluble gas, making it the correct answer in this context.