Why is it important to eat carbohydrates before running a marathon

How is the composition of a meteorite relevant to finding out the composition of earth's core?

When the volume and number of particles of a gas are constant which of the following is also constant

Three cards with holes are arranged in a straight line. a light is shined through the first card’s hole and travels through all three cards. what does this tell you about light rays? a) that light is reflected b) that light is refractive c) that light travels in a straight line d) that light does not travel in a straight line