Oil companies, mines, land.
Canada and Australia are now blocking these moves.
The US only allows noncontrolling interests.
Most other countries forbid foreign ownership outright.
Commodities have been plunging in value - except oil, and China owns the highest cost of extraction assets.
They are running out of available assets even as the market value of those assets diminishes.
Those assets rocketed in value largely because of Chinese demand - they top-ticked a declining market.
They are blocked from all of that. China could of course buy both Airbus and Boeing but they will never be allowed to. They can buy land in Africa, gold paper iou, or bonds. They are truly screwed. If the US dollar crashed their central bank would be bankrupt.