It is reported that North Korea has conducted another underground nuclear test.

We need to adjust the descent speed of the helicopter.

When you're ready, jump!

The snow is falling quietly.

Education about sex is very important.

In physics, the study of the 'nucleus' at the center of an atom is important.

We conducted a new experiment in science class.

Radioactive elements are produced in nature and scientific experiments.

Sufficient caution is necessary when handling radioactive materials.

This area is off-limits due to high radiation levels.