两个大小分别为F₁和F₂(F₂＜F₁)的力作用在同一质点上，它们的合力的大小F满足 [ ]

A．F₁≤F≤F₂

B．≤F≤

C．F₁－F₂≤F≤F₁＋F₂

D．F₁²－F₂²≤F²≤F₁²＋F₂²

Assuming inventory levels remain constant during the year and prices have been stable over time, COGS would be:（）

A. the same for both LIFO and FIFO.  

B. higher under the average cost than LIFO or FIFO.  

C. higher under the FIFO than LIFO or average cost.