sorry i could only do first answer
but here it is
Crossing-over is the exchange of genetic material between homologous chromosomes. It results in new combinations of genes on each chromosome. When cells divide during meiosis, homologous chromosomes are randomly distributed to daughter cells, and different chromosomes segregate independently of each other.
1I'm good
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The answer is gypsum as 2 is lower than 2.5 and since the other minerals are very hard, it would cause damage to the fingernail since the fingernail's hardness is 2.5.
