During which of the phases of growth, does the number of new cells balance the number of declining cells?

The correct answer is stationary phase.

Explanation:

There are four phases in a growth curve lag, log, stationary, and death phase. During the lag phase, cells adapt to the new environment and no growth occurs. During the exponential phase, cells grow at an exponential rate.

The stationary phase is the phase where the number of cells remains constant because the number of production of new cell becomes equal to the number of cell death. This phase shows that the culture reached its carrying capacity.

During the death phase, the number of cells starts declining because of the declining resources. Therefore the correct answer is the stationary phase.