Draw the structures of organic compounds A and B. Omit all byproducts. Compound A reacts with magnesium and ether to form compound B. Compound B reacts with acetaldehyde followed by water to form a 5 carbon chain where carbon 2 is bonded to O H.

North atlantic current or north atlantic drift is the answer

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.