Which of these signs is an example of a highway construction and maintenance sign

What color of light must blue light mix with to create white light? a. yellow b. white c. blue d. green

To run the physics cart, the fan speed of the cart is manipulated. this is the (blank) variable. the cart accelerates due to the speed of the fan. acceleration is therefore the (blank) variable. a “constant” is a parameter that stays the same regardless of the variables. one parameter of the cart that is held constant is the (blank) .

Idon’t quite understand this problem