Two separate errors sit in the underlined phrase. After the verb "help", the bare infinitive is required, so "help improving" is wrong and should read "help improve". Also, the word right before "health" must be the adjective "digestive", not the noun "digestion", since it describes the noun "health".
The correct replacement keeps "could help improve" with the bare infinitive and switches to the adjective "digestive", which is the given option (e), so the folded answer here is option 4.
If the price of a commodity increases by 25%, by what percentage should the consumption be reduced to keep the expenditure the same?