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gordon wrote this passage about mechanical waves for his physics class. but he got most of his facts mixed up. only one sentence is correct. which sentence is it?

a) mechanical waves don’t need a medium to travel. when they travel through a vacuum, mechanical waves are oval-shaped. they’re either transverse or double transverse waves.

b) mechanical waves can apply pressure to and push on objects in their path.

c) but they travel slower in denser mediums.

List the two type of transporst that the cell in orde to transport molecules acroos the membrane

1. suppose a reaction mixture, when diluted with water, afforded 300 ml of an aqueous solution of 30 g of the reaction product malononitrile [ch2(cn)2], which is to be isolated by extraction with ether. the solubility of malononitrile in ether at room temperature is 20.0 g/100 ml, and in water is 13.3 g/100 ml. what weight of malononitrile would be recovered by extraction with (a) three 100-ml portions of ether and (b) one 300-ml portion of ether? suggestion: for each extraction, let x equal the weight extracted into the ether layer. in part (a), the concentration in the ether layer is x/100 and in the water layer is (30 x)/300; the ratio of these quantities is equal to k 20/13.3.

What layer of the atmosphere is directly above the troposphere?