In the diagram below, two of the three rays used to find the image position are shown. Which of the following best describes the third (missing) ray?

A. A ray incident on a path that takes it through the left focus reffects
parallel to the axis.
B. A ray incident through the vertex continues through the lens
without refracting
C. A ray incident parallel to the axis refracts so that it passes through
the focus on the right hand side.

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me

moisture is lackin, and organic acids are scarce.