Environmental Science
Frost forms when:

The dew point is 32oF or below.
Water vapor changes into ice without first becoming a liquid.
All of these
Objects on the ground cool below the dew point temperature.

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Environmental Science
Definition of ecosystem is

The part of the earth and its atmosphere which inhibits living organisms
The community of organisms together with the environment in which they live
A community of organisms interacting with one another
The abiotic component of a habitat

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