Directions: The following sentence tests your ability to recognise grammar and usage errors. The sentence contains either a single error or no error at all. The sentence does not contain more than one error. The error, if there is one, is underlined and lettered. If the sentence contains an error, select any one from the underlined part that must be changed to make the sentence correct. If the sentence is correct, select choice (E). In choosing answers, follow the requirements of standard written English.

Sir James Dewar (A) invented the thermos (B) to keep heat away from the liquefied gas (C) with which he was (D) experiment. (E) No error