Explain how you know what type of selective pressure this is

you must remain stopped until the stop signal is retracted and the red lights are turned off. approaching traffic in the opposite roadway of a divided highway shall not be required to stop, even if the school bus has the stop-arm extended and the alternately flashing warning signal lamps on.

the answer is :

where in your body is there an enzyme that does function at a high or low ph? what is the name of that enzyme and its function?

sound moves fastest in solids because the molecules are tightly packed and it allows sound to vibrate