How many word roots does the term: have?

esophag/o/gastr/o/duoden/o/scopy

esophag – word root for esophagus

gastr – word root for stomach

duoden –  word root for duodenum

-scopy – suffix for visual examination

o – combining vowel used between word parts to ease pronunciation.

O is most often used as the combining vowel, so if you are stumped as to whether to use an o or a between esophag and gastr, go for the o.

Explanation:

answer; /// i believe the answer is (phenylketonuria);

d, i believe because of it's activity level