Question

What is the correct order of the development of the following?

1. Numerical control

2. Computer numerical control

3. Direct numerical control

4. Distributed numerical control

(a) 1, 2, 3 and 4              (b) 4, 2, 3 and 1

(c) 1, 3, 2 and 4              (d) 4, 3, 2 and 1