Because the seller of futures contracts has the option to deliver treasury bonds, the seller will generally choose the cheapest deliverable treasury bonds that are most beneficial to him and have the lowest delivery cost. This bond is the cheapest deliverable bond, and item A is correct. The price of the cheapest deliverable bond determines the price of the treasury bond futures contract, and item B is correct. Imp 1 iedreportate(IRR) refers to the interest rate yield obtained by buying spot treasury bonds and using them for futures delivery. Obviously, the national debt with higher implied repo rate is the cheapest deliverable national debt, and item CD is correct. So the answer to this question is ABCD.