Some of the sentences have errors and some are correct. Find out which part of a sentence has an error and corresponding to the appropriate letter (a,b,c). If a sentence is free from errors, corresponding to (d) in the correct sheet.
`("We have discussing")/a` `("all the known mechanisms")/b` `("of physical growth")/c` `("No error")/d`.

Explanation

(a) Replace .discussing. by .discussed.