His words carry importance.

This eigenfunction is one of the fundamental concepts of quantum mechanics.

This old radio uses a cold-cathode tube.

The launch of intercontinental ballistic missiles has become an international issue.

It is said that secondhand smoke has a negative impact on health.

Topology is a branch of mathematics that abstracts and generalizes the concept of space.

I love the class of reading Chinese classics in Japanese.

I studied Classical Chinese in university.

My friend goes to a Korean school.

He has already finished writing the report, so we use the present perfect form.