A term meaning "forming in the bronchi" is:
D. Bronchogenic
This term is composed of the root bronch(o) (any large air passage of lungs) and the suffix - genic (forming). Notice that when two word elements are combined, letters may be added or dropped so as to make the term easier to pronounce, as in this example where a combining vowel of "o" is added to the root "bronch."
In other instances, if the root word ends in a vowel, change that vowel to an "o" or simply add the combining vowel "o."
The vowels a, e, i, u and y may also be used as combining vowels. As examples: