Question

hydrosphere\tatmosphere
biosphere\tgeosphere
why would adding arrows to connect the four systems be useful for developing the model?
a. each system exchanges matter or energy with the other systems.
b. each system has temporary parts that may be replaced by another system.
c. matter and energy flow in one direction through all four systems.
d. living things may move among the four systems.

Explanation:

The question is about the Earth's systems (hydrosphere, atmosphere, biosphere, geosphere) and why arrows connecting them are useful. Option A states that each system exchanges matter or energy with others. Arrows in a model of these systems would represent these exchanges (e.g., water cycle between hydrosphere and atmosphere, nutrient cycles involving biosphere and geosphere). Option B is incorrect as parts of systems aren't "temporary" or replaceable by another system. Option C is wrong because matter and energy flow isn't strictly one - way through all systems (e.g., energy from sun to atmosphere to biosphere, but also energy transfer back in some forms, and matter cycles). Option D is about living things moving, which isn't the main reason for arrows connecting the four systems (arrows are about exchanges, not organism movement). So the correct answer is A.

Answer:

A. Each system exchanges matter or energy with the other systems.