Calcium carbonate is strongly heated until it undergoes thermal decomposition to form calcium oxide and carbon dioxide. The calcium oxide (unslaked lime) is dissolved in water to form calcium hydroxide (limewater). Bubbling carbon dioxide through this forms a milky suspension of calcium carbonate.
The colder something is the more the atoms are compressed together; atoms can't move as much. 35 degrees is the warmest option, so it makes the most sense.
