Questions about natural selection

25) a student takes four samples of a white crystalline solid and places each in a well plate. on top of each sample, she carefully places 20 drops of clear mystery liquids a, b, c and d. her results for each well are: liquid a: the solid dissolves quickly. liquid b: the solid appears unchanged. liquid c: a brownish colored liquid is produced. liquid d: fizzing occurs and the well becomes warmer. in which well does a physical change occur?

Im is in a crowd of people at the mall looking for his girlfriend tammy, who was supposed to meet him for dinner. jim realizes tammy is across the room as he catches a whiff of her overpowering perfume, 'paris #6'. which process explains why jim is able to smell the perfume?

Amap's orientation is typically determined by an