D. Genetic variation increases the likelihood of an allele being present that is best suited for the environment.
Answer:
Explanation: y’all taking the same test as me hahahahah I got the answers but I can’t attach the picture here so hit me up on snap daniela_0789
If I remember correctly (from my studies long time ago) the layers are from the outer to the center:
SiAl : Silicon-Aluminum
SiMa : Silicon-Magnesium (although should be Mg)
NiFe : Nickel-Iron
The SiMa layer should have the lightest elements (Magnesium is lighter than Aluminum)