Concept:Newton's first law of motion explains that a body continues in its state of rest or uniform motion unless acted upon by an external force.Explanation:The sun's gravitational pull provides the centripetal force that keeps the earth moving in its circular orbit.If this attraction suddenly ceases, no net external force acts on the earth.According to Newton's first law of motion, the earth will then continue moving in a straight line.This straight-line path is directed along the tangent to its original circular orbit at the point where the force disappeared.Answer:A. First law of motion