Can a light pass through a black paper?

When should a bar graph be used? a. when there is no independent variable. b. when the independent variable is continuous and does not show a relationship to the dependent variable. c. when the independent variable is continuous and shows a causal link to the dependent variable. d. when the independent variable is composed of categories and does not show a relationship.

Autotrophs a.consume their food to get energy b.may use photosynthesis to gain energy c.are also called consumers d.cannot use solar energy

Suggest why placing wheels under a heavy box reduces the neccessary force required to push it along at a constant speed.