I have been to Taiyuan.

The population is coming down.

The lifespan of this building is 50 years.

He clearly expressed his will and intentions.

The nuclear submarine advances quietly in the deep sea.

This building is the oldest wooden structure in existence.

This old building has survived the war.

The safety of nuclear reactors is very important.

We need to think about this problem in multiple dimensions.

What is the present value of this investment?