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?

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 : 

"Biorock technology" is talked about in which one of the following situations ?

The "Miyawaki method" is well known for the :