Answer: D) nutrients and other life-sustaining molecules are in limited supply and must be continually recycled Explanation: Biogeochemical cycles are crucial to ecosystem function because ::   1. Chemical elements are available in only limited amounts and must be recycled. 2. Nutrients and other life-sustaining molecules are in limited supply and must be continually recycled.

Answer: B) serving as the interface between the other spheres Explanation: The geosphere is the earth's solid rock or rigid outer layer known as the crust. Without the geosphere it would not be possible for humans to live on the planet. The function of the geosphere serving as the interface between the other spheres.

Answer: A) The most commonly thought of hazard in construction. This hazard includes radiation, extreme temperatures, noise, and vibration. Explanation: A physical hazard is defined as "A factor within the environment that can harm the body without necessarily touching it." Vibration and noise are examples of physical hazards.   Physical hazards include but aren't limited to electricity, radiation, pressure, noise, heights and vibration amongst many others.