How does the ductus arteriosus improve the efficiency of fetal circulation?

Check all that apply diatoms are marine algae that have a shell made of silica, what are some of the uses of the silica shell after the diatoms die? 1.the shells make up the diatomaceous earth used in filters 2.it can be used as an ingredient in abrasives 3.they are used in food products 4.the shells can be used in some insulating materials

Other than earth, is also known to have magnetic pole reversal? a: venus b: mars c: earths moon d: the sun

Which ocean is on the eastern coast of north and south america? arctic ocean indian ocean pacific ocean atlantic ocean