A word used to describe an action, state, or occurrence, and forming the main part of the predicate of a sentence is a verb. In this particular sentence, we would be using a verb to fill the blank. Since a single thing has been described thus we would use a singular verb
"Has" is a singular verb. It is the right option
"Have" is a plural verb. This is the wrong answer
“Does” is the third person singular present tense of the verb “do.” It is used when referring to a person or a thing in the third person.
Now, has and have means to possess something, whether a condition, a physical object, a mental concept, etc.
Whereas do and does mean a form of action, and changes form with the pronouns. In this sentence, a condition has been explained. Thus, has is the correct answer
Option B is correct.