Choose the grammatically correct sentence:

The correct answer is Option (3) → We did not have much time, so we ate at the station canteen.

Much with an uncountable noun:

• “Much” is used with nouns we cannot count.
• “Time” here means a length of time. It cannot be counted, so “much time” is correct.

Why the Other Options are Incorrect?

Option 1: Before my board exams, Nani gave me an advice that I still follow. — Incorrect. “Advice” cannot be counted, so it cannot take “an”. To speak of one, we use the unit word “a piece of”.
Corrected: Before my board exams, Nani gave me a piece of advice that I still follow.

Option 2: There were not much chairs left in the hall for the parents. — Incorrect. “Chairs” can be counted. So it takes “many”, not “much”.
Corrected: There were not many chairs left in the hall for the parents.

Option 4: The cows gave fewer milk during the hot summer months. — Incorrect. “Milk” cannot be counted. So it takes “less”, not “fewer”.
Corrected: The cows gave less milk during the hot summer months.