If you gonna answer give all the answers :-)

3is a crest4 is a trough 2 is the amplitude 1 is the wavelength

Answer (d) the universe had cooled enough for atoms to combine, protons and neutrons were too far apart to form nuclei;

It was crowded with sewer like smells. bad sewer systems

In the conservation of mass, mass (which is the same as energy) can never be created or destroyed in the same way oil is formed from the remains of small animals and plants that died and fell to the bottom of the sea and their mass (energy) is conserved as oil.