Coitus interruptus is one method of contraception, but it is not completely reliable.

There are many introduced species of plants living in this park.

He engaged in an extravehicular activity from the spaceship.

He is undergoing training for extravehicular activity.

He is a foreigner, but he can speak Japanese fluently.

This book explains in detail about the use of foreign words.

He thought deeply and said, 'I think, therefore I am.'

He strongly believes in the philosophical thought, 'I think, therefore I am.'

He checked whether he remembered or not.

He always acts with a spirit of sincerity and compassion.