Which two fixatives are stated to both contain formaldehyde?

• A. B-5 and Orth
• B. Zamboni and Zenker
• C. Orth and Zenker
• D. B-5 and Zamboni

Answer: (A)

Formaldehyde-containing fixatives are aldehyde-based cross-linkers that preserve tissue by cross-linking proteins. Among the options, both B-5 and Orth's fixatives include formaldehyde in their formulations, so they contain the aldehyde used for fixation. The other two fixatives listed do not rely on formaldehyde in their standard formulations, since Zenker’s uses mercuric chloride and chromates with acetic acid, and Zamboni’s is typically a picric-acid–based fixative without formaldehyde. Therefore, the pair that contains formaldehyde is B-5 and Orth.