An engine’s iron cylinder is to be inserted into a block of aluminium. The outside diameter $M$ of the iron cylinder is just a little greater than the diameter $N$ of the hole in the aluminium. Which action would be best to allow the cylinder to fit into the aluminium?
- ACool the aluminium and cool the iron.
- BCool the aluminium and heat the iron.
- CHeat the aluminium and cool the iron.
- DHeat the aluminium and heat the iron.