His mettle shows that he never gets discouraged even in difficult situations.

He likes to take a walk in the park at dusk.

This diode only allows current to flow in one direction.

The vas deferens is a part of the male reproductive system and has the role of transporting sperm.

This old radio uses a vacuum fluorescent display.

He is mindful of healthy eating and exercise to reduce the risk of cardiovascular disease.

This old radio uses a pentode.

This old radio uses a cold-cathode tube.

Inside the ear, there are semicircular canals to maintain balance.

The urachus is a structure that exists during the fetal period, connecting the bladder and the navel.