d) option is correct
Step-by-step explanation:
The stringent response occurs in response to low energy store
For example when there is low level of lactose it means energy level is low so there will be no transcription of genes and hence transportation and catabolism of lactose will be inhibited
When E coli is grown in mixture of both glucose and lactose, at high glucose concentration the growth rate is maximum and lactose catabolism is repressed, this called as catabolite repression and it is due to level of cAMP