Answer:
Patau's syndrome
Explanation:
Patau's syndrome is a genetic disorder caused by one additional chromosome 13, and therefore it is an aneuploidy caused by an extra chromosome (i.e., a trisomy). Individuals with Patau's syndrome have 47 chromosomes instead of 46 in some or all their somatic cells. This syndrome seriously affects fetal development, usually resulting in miscarriage, stillbirth or in neonatal death. The incidence of this syndrome is around 1/5,000 births.
Sound would travel faster in a thick piece of metal since the molecules are closer together. However, since there are more molecules, it would be quieter on the other side than the hollow metal.
The studies are designed this way b/c it removes the power of suggestion and the double-blind study keeps both researchers and participants in the dark. So this compared to who is receiving the treatment which is relevant b/c it stops the researchers from accidentally overbalancing the study participants, or unintentionally favoring their assessment of the conclusions.