All animals need oxygen. we get oxygen from the air we breathe. how do fish get theirs?

I'm thinking it's 2 you are asked to explain the earth's magnetic field. which is the best reply? 1. the earth's magnetic south is similar to the north pole of a magnet. 2. the earth's core has a strong magnetic charge similar to the south pole of a magnet. 3. the earth's geomagnetic south is similar to the south pole of a magnet. 4. the earth's magnetic charge is not centered at either pole; it varies based on location.

How to tell if a molecule is polar or nonpolar with electronegativity

If the textbook weighs 19.6 newtons on venus,what is the strength of gravity on venus?