Which level of biodiversity involves variations within a single population

Wo audio speakers are placed on a vertical rail. speaker a is placed at head-level while speaker b is place at some variable height, \delta yδy, above speaker a. both speakers receive simultaneous input from a sine-wave generator so the speakers each produce a pure sinusoidal sound wave with a wavelength of 0.531 meters. calculate the lowest height that speaker b can be placed above speaker a to produce a minimum of sound heard by person standing \delta x = 7.86δx=7.86 meters directly in front of speaker a.

The transfer of heat through the movement of a gas or liquid a. convection b. conduction c. radiation

The difference between a red shift and a blue shift has to do with wavelength frequency. t or f