This compound has a tetrahedral molecular geometry.

The Riemann sum is a method for approximately calculating the integral of a function.

He is playing the character of Bun.

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.

My friend goes to a Korean school.

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

He was infected with hepatitis E.