The clearing house will determine WHO to deliver but will not tell you any name. They will tell you WHERE to deliver. It is my jobQ 66 is "Market order" as Lesnar pointed said "QUICKLY" thats the key. Hall mark of the exam was for the non numerical questions you could eliminate 2 options quickly other two option required some bit of deep thinking and was often tricky. Imp it did test key ideas.
Q 75 agree with @babyik , short will deliver as late as possible in case of falling prices. Clearing house will determine WHO to deliver.