Question

which of the following best explains why the water cycle is considered a closed system?
water only moves in one direction
the total amount of water on earth remains constant
water cannot escape earths atmosphere
all water eventually returns to the oceans

which human activity has the greatest impact on the water cycle?
agriculture
urbanization
dam construction
deforestation

which of the following is considered a reservoir in the water cycle?
precipitation
evaporation
runoff
ocean

Explanation:

First Question

A closed system in terms of the water cycle means the total quantity of water within the Earth's system (atmosphere, hydrosphere, etc.) doesn't change. Option 1 is wrong as water moves in multiple directions. Option 3 is incorrect because some water can escape (though minimally, but the key for closed system is total amount constant). Option 4 is wrong as water can be in other reservoirs like glaciers. The total amount of water on Earth remaining constant (Option 2) explains it's a closed system.

Deforestation affects transpiration (trees release water vapor), which is a key part of the water cycle. Agriculture, urbanization, and dam construction impact the water cycle too, but deforestation has a broad and significant effect on the overall cycle by reducing transpiration, altering runoff, and affecting precipitation patterns.

A reservoir in the water cycle is a place where water is stored. Precipitation, evaporation, and runoff are processes, not storage areas. The ocean is a large storage (reservoir) of water in the water cycle.

Answer:

B. The total amount of water on Earth remains constant

Second Question