What begins the combustion phase of a four-stroke engine cycle? A. The air-fuel mixture is compressed.
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B. An air-fuel mixture flows into the cylinder.
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C. The air-fuel mixture is ignited.
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D. The air-fuel mixture expands.

In the particles are arranged in a regular, repeating pattern. a)a crystalline liquid b)a crystalline solid c)all gases d)all solids

What will most likely happen in the absence of a cell membrane? a) photosynthesis will not take place. b) the cell will not store food, water, nutrients, and waste. c) energy will not be released during cellular respiration. d) substances will pass in and out of the cell in an uncontrolled manner.

Condensation happens when water vapor cools. true or false? ?