The key identifying feature of a resource$-$allocation problem is which of the following?

I. Constraints with the form "Amount of resource used $$ Amount of resource available".

II$.$ Constraints with the form "Amount of resource used $$ Amount of resource available".

III. Constraints with the form "Level achieved $$ Minimum acceptable level".

IV$.$ All constraints have the form "Amount provided $=$ Required amount".

Multiple Choice

III only

IV only

At least two of I, II$,$ and IV$.$

I only

$19$ of $40$