Read the sentence given below to find out if it contains any error. The error, if any, will be in one part of the sentence. If the sentence is error free, select No error or option 5. Ignore error of punctuation if any.

The whitest-ever paint has been (A)/ produced by academic researchers, (B)/ with the aim of boost the cooling (C)/ of buildings and tackling the climate crisis.(D)/ No error (E)