Pick up the correct statement from the following: A. The basic length of a runway is increased at a rate of 7% per 300 m of elevation of M.S.L. B. The standard temperature at the site is obtained by reducing the standard sea level temperature of 15°C at the rate of 6.5°C per 1000 m rise in elevation C. The aerodrome reference temperature is the monthly mean of the mean daily temperature for the hottest month of the year D. All the above

The correct answer is D. All the above.

The basic length of a runway is increased at a rate of 7% per 300 m of elevation of M.S.L. This is to account for the fact that the air is thinner at higher altitudes, which means that an aircraft will need to travel further to take off and land.

The standard temperature at the site is obtained by reducing the standard sea level temperature of 15°C at the rate of 6.5°C per 1000 m rise in elevation. This is to account for the fact that the air is cooler at higher altitudes.

The aerodrome reference temperature is the monthly mean of the mean daily temperature for the hottest month of the year. This is used to determine the required length of a runway, as well as the required performance of an aircraft.

Therefore, all of the statements are correct.