Reference: the action of alluding or mentioning something; source; things that you have used for an assignment
A. Syphilis is a communicable disease. The others are diseases originating from within the body.
If you accept either C or D as the correct revision then you have to accept both of them. Hence the best way to treat the sentence is to ignore both of them.
B is not correct either. You can over punctuate.
That leaves A.
Sometimes the right answer to many things is to do nothing. My dad used to say "Don't fix what isn't broke."
A is the answer <<<<<
Prepositional is a word that expresses a relationship between a noun/pronoun and another word in a sentence. Easier way to put it would be like saying you take a object or noun (ex: home) and also make up a location (ex: in), basically noun relation to a verb.
Example: <u>In my house</u>, you'll find my dog. House relates to where the dog is.
