【单选题】When something is on fire. People throw sand (沙子) on it to put out the fire. The main use of the sand is to ________. [ ]
A.
protect the thing on fire.
B.
add weight to the thing on fire.
C.
keep the air away from the thing on fire.
D.
lower the temperature of the thing on fire.
【单选题】使用最小二乘法拟合时间数列的趋势线,为了简化计算,可采用简捷法来求趋势线中的参数 a 、 b ,首先必须先假定( )。
【单选题】When something is on fire, people throw sand (沙子) on it to put out the fire. The main use of the sand is to _____. [ ]
A.
protect the thing on fire
B.
add weight to the thing on fire
C.
keep the air away from the thing on fire
D.
lower the temperature of the thing on fire