Question

According to the correspondence principle:

(a) new theory must agree with old theory where they overlap.
(b) Newton's mechanics is as valid as Einstein's mechanics.
(c) relativity equations apply to high speeds while Newton's equations apply to low speeds.
(d) special relativity and general relativity are two sides of the same coin.

Answer 1

(a) new theory must agree with old theory where they overlap

Example: at low speeds relativistic theory must agree with the original Newtonian theory