激光在焊接过程可以在空气环境中进行，因此保护气体在激光焊接中可有可无。
参考答案：错
A firm realizes that it is producing more than the profit maximizing level of output and makes a short-run decision to decrease its output. Which of the firm's cost measures is least likely to decrease as a result（）
A. Average variable cost.
B. Average total cost.
C. Average fixed cost.
中美《望厦条约》规定，美国兵船可任意到中国各通商港口“巡查贸易”；美国人有权在通商口岸“开设医院，建立教堂”等。英国凭借特权可以享受这一待遇。英国享受的特权是指（）
A.片面最惠国待遇
B.领事裁判权
C.协定关税
D.在通商口岸租赁房屋
