The correct choice is (a) Lag phase
For explanation I would say: During batch culture, a typical bacterial growth curve shows five distinct phases of growth: lag phase, the delay before the start of exponential growth; exponential phase, where cell division proceeds at a constant rate; stationary phase, when conditions become unfavorable for growth and bacteria stop replicating; death phase, when cells lose viability; and, finally, long-term stationary phase, which can extend for years. It has been assumed that lag phase allows the adaptation required for bacterial cells to begin to exploit new environmental conditions. This process could include the repair of macromolecular damage that accumulated during stationary phase and the synthesis of cellular components necessary for growth.