What is the importance of oceanic and continental waters?

Why does a tidal bulge occurs on opposote sides of earth

[ou.01]which of these is the most likely use of an electromagnetic wave which has wavelength shorter than microwaves but longer than visible light? o heat food safely o neat food safely o take images of bones and teeth o transmit radio and cellular phone signals o take images of bones and teeth o transmit radio and cellular phone signals o detect the location of objects which emit heat

Can someone me choose a broad topic and area of focus i am really doing this as a tally to see which one most people pick ok water pollution global warming endangered species atmosphere for the !