Which of the following best describes parent rock?
a)crushed gravel added to depleted soil to provide nutrients

b)the lowest layer of the soil horizon, containing little or no organic matter

c)high-nutrient igneous rock like obsidian, extruded from the earth’s magma

d)the primary stone sheet from which a boulder or stone originated

Suppose a force of 60 n is required to stretch and hold a spring 0.1 m from its equilibrium position. a. assuming the spring obeys hooke's law, find the spring constant k. b. how much work is required to compress the spring 0.5 m from its equilibrium position? c. how much work is required to stretch the spring 0.6 m from its equilibrium position? d. how much additional work is required to stretch the spring 0.1 m if it has already been stretched 0.1 m from its equilibrium? a. kequals 600