Which combining form denotes green or association with chlorine?

• A. Dur/o
• B. Chlor/o
• C. Gingiv/o
• D. Nat/o

Answer: (B)

Chlor/o denotes green or association with chlorine. This combining form comes from the Greek chloros, meaning greenish-yellow, and the element chlorine was named for that same greenish color. So terms built with chlor/o signal either the color green (like chlorophyll, which gives plants their green color) or the element chlorine itself (chlorination, chlorides). The other options don’t carry that meaning: dur/o means hard, dural; gingiv/o refers to the gums (gingiva); nat/o relates to birth.