Which programming language is designed for the instruction of youngsters

A．began using binary numbers
B．was used to implement the Unix operating system
C．was put into the market
D．was used for modeling physical and environmental events

A．The focus on the bird is an important yet missing characteristic, and without it even the successful discovery will seem hollow.
B．It is not the bird but the human efforts that attract a lot of readers' attention.
C．The article argues that the book is with great content and great focus.
D．Although the book is not stylish, readers still find interesting things in its characterization and extended hist0ry of the bird.