The hyphen is used to form the unit. In this choice, the use of the hyphen is required. The hyphen should NOT be used. This choice is the correct answer. Below is a portion of a letter which you must proofread looking for typographical, spelling, punctuation and grammatical errors.
Typographical errors can include omissions, repetitions, double strikes, or transpositions.
The question that follows concerns the possible errors in the passage. The Water Pollution Control Board, a newly created agency, is in need of business stationery. I am having difficulty choosing among the many varieties described in your brochure. It would be most helpful if a representative of your company could visit me to show me samples of your line. Make no changes.