Final answer:
The speed of light in a vacuum is 300 million meters per second (3 × 10⁸ m/s), which is a fundamental constant in Physics.
Step-by-step explanation:
The speed of light across space is a fundamental physical constant that is of great importance in the field of Physics. It is denoted by the symbol 'c' and has a value of 300 million meters per second (m/s) or, more precisely, 2.99792458 × 10⁸ m/s, which can be approximated to 3 × 10⁸ m/s for most practical purposes. This value applies when light is traveling through a vacuum.
Therefore, the correct answer for the speed of light across space is 'c' - 300 million meters per second.