When a cell is actively growing, the arg operon is , and arginine is .

The correct answer is - on, actively synthesize.

Explanation:

The arg operon is a negative regulator that releases or regulates the production of arginine in only the presence of arginine. Attaching the arginine to the arginine repressor protein causes the repressor to bind to the operator sequence.

When a cell is growing actively this operon is on and the synthesis of arginine in this cell is continuous. Arginine induces a conformational change in the protein structure.

answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.