The rise of the US dollar index indicates that the US dollar appreciates and the purchasing power increases. Crude oil is denominated in US dollars, so the price of crude oil will rise. But this is only a theoretical formulation, and sometimes the price of crude oil and the dollar index rise at the same time. Therefore, the appreciation of the US dollar is not necessarily the only factor for the decline in crude oil prices, and crude oil prices are also affected by inventory and demand factors.