Explanation:

- The sentence revolves around comparing Neha's pay in relation to her work quality or quantity.

- Option 1: "too highly" is an incorrect option because it implies overpraise or excessive value, rather than adequacy.

- Option 2: "high enough" is correct as it suggests sufficiency or adequacy, which fits well with the context of pay being equitable for her work.

- Option 3: "much high" is grammatically incorrect; "much higher" or "very high" would be appropriate forms.

- Option 4: "enough high" is also grammatically incorrect because "enough" typically follows the adjective in English phrasing.