A.I. Explanation:

Correct answer: challenges

Explanation: The word 'challenges' fits grammatically as a plural noun that complements the phrase 'new ideas.' It aligns contextually with the notion of a postgraduate environment where students are expected to face and overcome difficulties.

Meaning: 'Challenges' refers to difficulties or obstacles that require effort to overcome.

Wrong options:

• best: 'Best' is an adjective that does not fit in this context as it does not relate to the idea of facing difficulties.
• promoting: 'Promoting' is a gerund that implies an action of support or encouragement, which does not fit the context of encountering new ideas.
• reasons: 'Reasons' is a plural noun that refers to explanations or justifications, which does not align with the context of facing difficulties alongside new ideas.

Correct answer: major

Explanation: The term 'major' is an adjective that describes the noun 'issues,' indicating that they are significant or important. This fits both grammatically and contextually within the sentence about sustainability issues.

Meaning: 'Major' means significant or important, indicating the level of impact of the sustainability issues being addressed.

Wrong options:

• best: 'Best' is an adjective that does not appropriately describe 'issues' in this context, as it implies superiority rather than significance.
• challenges: 'Challenges' is a noun that does not fit here as it does not describe the type of issues being tackled.
• promoting: 'Promoting' is a gerund that does not function as an adjective and does not describe the issues at hand.

Correct answer: strong

Explanation: The word 'strong' is an adjective that describes the noun 'demand,' indicating a high level of need or requirement for graduates. This fits grammatically and logically within the context of employer demand.

Meaning: 'Strong' indicates a high level of intensity or force, in this case, referring to the significant demand for graduates.

Wrong options:

• best: 'Best' is an adjective that does not fit the context of demand, as it implies superiority rather than intensity.
• challenges: 'Challenges' is a noun that does not describe the nature of demand and is therefore irrelevant in this context.
• major: 'Major' is an adjective that does not appropriately describe 'demand' and does not convey the intended meaning of intensity.