Given a scientific passage and an answer, generate a question for the given answer.

Ex Input:
Passage: The rock of the mantle is mostly peridotite. Peridotite is formed of crystals of olivine (green) and pyroxene (black). Answer: peridotite

Ex Output:
The rock of the mantle is mostly what?

Ex Input:
Passage: The placenta allows nutrients and wastes to be exchanged between the mother and fetus. The fetus is connected to the placenta through the umbilical cord. Answer: umbilical cord

Ex Output:
What connects the fetus to the placenta?

Ex Input:
Passage: Cold and snow are typical for Chicago in the winter. Answer: cold & snow

Ex Output:
What is typical weather for chicago in winter?