[单选题]
When the engine of your car heats qx0+rjky*0a vz yg8 hb,k9y z6dof 78gup, the spark k.w*+no9. cr-rzqcys plug gap will
A. increase.
B. decrease.
C. remain unchanged.
D. decrease at first and then increase later, so that the two effects cancel once the engine reaches operating temperature.
