The type of contract where the buyer incurs opportunity cost but little or no additional cost risk is called______.

A) fixed-price with incentive
B) firm-fixed-price
C) fixed-price with economic price adjustment
D) fixed-price with right of renewal

如图是某种物质凝固时温度随时间变化的图像。由图可知：此种物质为__________（填 “晶体”或“非晶体”），判断的依据是 ______________。该物质的凝固点为___________℃。