Please i need this asap please

The chart shows the bid provided by four contractors to complete a job. which contractor is the most cost-effective?

Which sentence about particles in matter is true? a. atoms are present in solids and liquids but not in gases. b. the particles of matter are in constant motion. c. the same kinds of atoms are found in different elements. d. when a solid changes to a liquid, the sizes of the particles change.

Imagine that you push on a large rock. at what point does your effort change the rock’s mechanical energy?