Answer:
B. fused sentence.
Explanation:
A fused sentence is an example of two fused sentences where there is a missing conjunction or punctuation mark to separate them. This is a mistake and should be avoided.
In the example given, there is a period missing. Another version is necessary:
Julie is a real hypochondriac. When her stomach hurts, she is certain that she has a bleeding ulcer, and if she has a backache, she believes that she has cancer of the spine.
