Read the given sentence to find out whether there is any grammatical or idiomatic error in it. The error, if any, will be in one part of the sentence. The corresponding letter of that part is the answer. If the given sentence is correct as it is, then choose option ‘No error’ as the answer response. (Ignore errors of punctuation, if any).

Although securing a permanent license (A) / for the new facility proved to be a (B) / tedious process, but the team successfully completed (C) / all the necessary compliance requirements (D).