In the context of WHO Air Quality Guidelines, consider the following statements :

1. The 24-hour mean of PM_2.5 should not exceed 15 μg/m³ and annual mean of PM_2.5 should not exceed 5 μg/m³.

2. In a year, the highest levels of ozone pollution occur during the periods of inclement weather.

3. PM₁₀ can penetrate the lung barrier and enter the bloodstream.

4. Excessive ozone in the air can trigger asthma.

Which of the statements given above are correct?

With reference to "Gucchi" sometimes mentioned in the news, consider the following statements :

1. It is a fungus.

2. It grows in some Himalayan forest areas.

3. It is commercially cultivated in the Himalayan foothills of north-eastern India.

Which of the statements given above is/are correct?

Which of the following are nitrogen-fixing plants ?

1. Alfalfa

2. Amaranth

3. Chickpea

4. Clover

5. Purslane (Kulfa)

6. Spinach

Select the correct answer using the code given below :