Iput it in the wrong category !
pls

which describes a difference between birds and mammals?

birds protect and feed their young.

birds have nearly hollow bones.

birds undergo internal fertilization.

birds efficiently transport oxygen to cells.

Birds have nearly hollow bones

birds have nearly hollow bones

Explanation:

Their bones are nearly hollow which greatly reduce their weight and allow them to fly

r = ρ x length / area  

ρ = r x area / length  

ρ is in ohm-meters  

in basic units, it is m³kg/s³a²  

i think this is it.

the doppler effect is used by weather forecasters to measure 

moving clouds