Meaning: 'Cast' means to throw or project something, in this case, doubt onto opponents.

Wrong options:

• susceptibility: This noun refers to the state of being likely to be influenced or harmed, which does not fit the action of creating doubt.
• credibility: This noun refers to the quality of being trusted and believed in, which does not fit as an action in this context.
• express: This verb means to convey a thought or feeling, which does not align with the action of creating doubt.
• business: This noun refers to a commercial activity, which is unrelated to the context of casting doubt.

Correct answer: credibility

Explanation: The noun 'credibility' refers to the quality of being trusted or believed in, which is relevant in the context of discussing media organizations. It fits grammatically as it serves as the object of the preposition 'on.'

Meaning: 'Credibility' means the quality of being convincing or believable.

Wrong options:

• susceptibility: This noun refers to the likelihood of being affected by something, which does not fit the context of media trustworthiness.
• cast: This verb does not fit here as it does not describe a quality or state of being.
• advent: This noun refers to the arrival of something, which does not relate to the trustworthiness of media organizations.
• proliferate: This verb means to increase rapidly, which does not fit as it does not describe a quality of media.
• express: This verb means to convey a thought or feeling, which does not fit in this context.
• business: This noun refers to a commercial activity and does not relate to the concept of trust or belief.

Correct answer: advent

Explanation: The noun 'advent' refers to the arrival or beginning of something significant, which is appropriate in the context of discussing the emergence of social media. It fits grammatically as it serves as the subject of the clause.

Meaning: 'Advent' means the arrival or introduction of something important.

Wrong options:

• susceptibility: This noun refers to the state of being likely to be influenced, which does not fit the context of the arrival of social media.
• credibility: This noun refers to the quality of being trusted, which does not fit as it does not describe an arrival.
• cast: This verb does not fit as it does not describe a noun or arrival.
• proliferate: This verb means to increase rapidly, which does not fit as it does not describe an arrival.
• express: This verb means to convey a thought or feeling, which does not relate to the concept of arrival.
• business: This noun refers to a commercial activity and does not relate to the emergence of social media.

Correct answer: proliferate

Explanation: The verb 'proliferate' means to increase rapidly in number, which fits contextually as it describes how fake news stories spread through social media. It fits grammatically as it follows the structure of the sentence requiring a verb.

Meaning: 'Proliferate' means to grow or increase rapidly.

Wrong options:

• cast: This verb means to throw or project, which does not fit in the context of spreading news.
• advent: This noun refers to the arrival of something, which does not fit as it does not describe an action of spreading.
• susceptibility: This noun refers to the likelihood of being affected, which does not fit as an action.
• credibility: This noun refers to the quality of being trusted, which does not fit as it does not describe an action.
• express: This verb means to convey a thought or feeling, which does not fit in the context of spreading news.
• business: This noun refers to a commercial activity and does not relate to the action of spreading.