Read each sentence to find out whether there is any grammatical error in it. The error, if any will be in one part of the sentence. The letter of that part is the answer. If there is no error, the answer is 'D'. (Ignore the errors of punctuation, if any).

1. A large scale exchange of nuclear weapons
2. will produce unprecedented amounts of radiation
3. that can penetrate into the biological tissue.
4. No error.