The correct answer is C) The doctors finally realized that Janelle has diabetes, a disease that affects the body’s blood sugar.
Step-by-step explanation:
The purpose of combining two or more sentences is to create a new sentence by putting together the key information of the original sentences in a concise, coherent, and clear sentence. In this case, sentence 5 "This disease affects the body’s blood sugar" relates to sentence 4 because this explains what diabetes is. Due to this, the information about diabetes altering blood sugar needs to be added to the first sentence.
The best way to do this is "The doctors finally realized that Janelle has diabetes, a disease that affects the body’s blood sugar" because this integrates the information of both sentences omitting unnecessary words such as "a diseases called"; also, connecting the information of sentence 5 with a comma is grammatically correct, and makes the sentence to flow in all the paragraph. This is important because other options have punctuation mistakes or do not organize information properly.