He is immersed in the study of geometrical optics.

There are no aspirated consonants in Japanese.

An aspirated consonant is a sound that is pronounced with a strong exhalation.

Please ensure the safety around you when using fire at the camp.

He is behaving like an idiot.

Chlorine detonating gas is very dangerous, and it requires careful handling.

He scooped up water with his hand and drank it.

He likes repairing old locomotives.

Oligodendrocytes play a role in supporting the nerve cells of the central nervous system.

The World Health Organization is working to improve public health worldwide.