Which of the following is not poisonous?

H₂O

The correct answer is option 1. \(H_2O\).

\(H_2O\), or water, is a colorless, odorless, and tasteless liquid that is essential for life. It is not poisonous and is actually very important for our health.

\(H_2S\), \(H_2Se\), and \(H_2Te\) are all poisonous gases. \(H_2S\) is known as hydrogen sulfide, and it is a colorless gas with a strong odor of rotten eggs. It is very toxic and can be fatal if inhaled. \(H_2Se\) is known as hydrogen selenide, and it is a colorless gas with a pungent odor. It is also very toxic and can be fatal if inhaled. \(H_2Te\) is known as hydrogen telluride, and it is a colorless gas with a garlic-like odor. It is also very toxic and can be fatal if inhaled.

Therefore, the only non-poisonous substance in the list is \(H_2O\).