Directions (26-30): In each of the question given below, a statement has been given with a blank. Some words or phrases have been given in the options following the statement. Choose the most appropriate word or phrase that could fit in the statement to make it contextually meaningful and grammatically correct.

Biosphere reserves are ___________ for the future of our planet.

To determine the most appropriate word to fill in the blank, let us analyze the context of the sentence and the meanings of the given options:

The sentence is: "Biosphere reserves are ___________ for the future of our planet."

Let's evaluate each option:
1. tired: This word means feeling a need for rest or sleep. It makes no grammatical or contextual sense when describing biosphere reserves.
2. inactive: This word means not engaging in or involving physical activity or action. Biosphere reserves are active areas for conservation and research, so calling them "inactive" for the future of our planet is contextually incorrect.
3. unique: While biosphere reserves are special, saying they are "unique for the future" is contextually weak compared to expressing their necessity or importance.
4. vital: This word means absolutely necessary or important; essential. Biosphere reserves play an essential role in conserving biodiversity and ensuring ecological balance, making them crucial or "vital" for the future of our planet.

Thus, the word "vital" fits the blank perfectly, making the sentence grammatically correct and contextually meaningful.

Therefore, the correct answer is vital.