Which statement exemplifies abstraction$?$

a$.$

A convenient way to view the hardware component called "memory" is to focus on the billions of electronic devices that go into constructing a memory unit.

b$.$

The president of General Motors views the company in terms of its corporate divisions and high$-$level policy issues.

c$.$

A good approach to algorithm design and software development is to focus on how we might actually implement a particular operation.

d$.$

The president of General Motors views the company in terms of every worker, every supplier, and every car.