Which of the following is an identifying characteristic of chlorine gas?

Chlorine gas is well-known for its distinct choking smell, which is a key characteristic that helps in its identification. This sharp, pungent odor is often described as similar to the smell of bleach, a compound that contains chlorine. It serves as a warning sign of the presence of chlorine gas, which can be hazardous to health when inhaled in significant quantities. Recognizing this odor is crucial for safety, especially in environments where chlorine is used, such as in swimming pools or industrial applications.

The other options do not accurately describe chlorine gas. For instance, it does not have a sweet or earthy smell, and it is certainly not odorless. Understanding these characteristics is essential when handling or responding to chlorine gas situations.