Which of the following gases is tasteless, odorless, and colorless?

The correct answer is nitrogen. Nitrogen is a diatomic molecule that makes up about 78% of the Earth's atmosphere. It is indeed tasteless, odorless, and colorless, which makes it an inert gas that is both safe and abundant. This characteristic is important for many applications, including its use in food packaging to displace oxygen and prolong shelf life, as well as its role in various industrial processes.

In contrast, the other gases listed have distinguishing properties. Carbon dioxide has a slight acidity and is detectable by taste and smell, particularly in higher concentrations. Methane, while mostly tasteless and odorless, can be detected through the odorant that is often added to it for safety purposes. Oxygen is also colorless and odorless but is essential for respiration and combustion, making it an active participant in chemical reactions. Thus, nitrogen remains the only gas in this list that fits all three criteria perfectly.