Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

Question: While similar to insects, what eight-legged invertebrates lack antennae or wings? Answer: arachnids
Arachnids do not have antennae or wings.

Question: The rock of the mantle is mostly what? Answer: peridotite
The rock of the mantle is mostly peridotite. Peridotite is formed of crystals of olivine (green) and pyroxene (black).

Question: What type of diagnosis happens before a baby is born? Answer: prenatal
Prenatal diagnosis refers to the diagnosis of a disease or condition before the baby is born.