The stringent response a. ensures that the cell has a large number of ribosomes for translation. b. occurs in response to sugars other than glucose and ensures that the cell only transcribes catabolic operons when the appropriate sugar (such as lactose) is present. c. is a form of catabolite repression. d. occurs in response to low energy stores.

d) option is correct

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