Select the option from each drop$-$down that best completes the corresponding sentence.

The Big Bang theory is a fascinating theory about our Universe that states that the Universe began sometime about $14$ billion years ago. The theory rests on our current understanding of physics and on observations that demonstrate that the Universe is cooling with time as it expands. The reason why the first era is called the Planck era $($after the physicist Max Planck$)$ is because at the time scale of $10-43$ seconds, the current physics we know of for tiny distances $($the Universe as a dot$)$ and short time scales would be dominated by Answerparticleunified forcequantum effects. Because of this, such large energy Answerfluctuationsvaluesparticles would require a theory that merges Answerquantum mechanics and general relativitygeneral relativity and special relativityquantum theory and special relativity $-$ this is unfortunately a theory we do not have.