Verbs and Verb Phrases

People have held athletic competitions since the time of the ancient Greeks.

Ever since the days of ancient Greece, athletes have been competing in many sports.

Track-and-field events have been very popular for a long time.

In one type track event, an athlete must leap over hurdles.

A good hurdler should have speed, rhythm, and balance.

A successful hurdler should also move with long strides.

Of course a hurdler will have practiced for many hours before an important race.

Other great athletes may have trained for years for a specific track event.

What is the subject of the following sentence?

One of the other reindeer invites Rudolf to play soccer, a favorite reindeer game.