Distilled water is neutral, because the H+ and OH- ions are balanced. Litmus is a natural acid-base indicator extracted from a type of lichen.
Answer: Option D is correct.
Explanation: Equation given by de Broglie is:

where,
= wavelength of the particle
h = Planck's constant
m = mass of the particle
v = velocity of the particle
In option A, football will have some mass and is moving with a velocity of 25 m/s, hence it will have some wavelength.
In Option B, unladen swallow also have some mass and is moving with a velocity of 38 km/hr, hence it will also have some wavelength.
In Option C, a person has some mass and is running with a velocity of 7 m/hr, hence it will also have some wavelength.
As, the momentum of these particles are large, therefore the wavelength will be of small magnitude and hence, is not observable.
From the above, it is clearly visible that all the options are having some wavelength, so option D is correct.
Because, at lower elevation, everything is tightly packed, and theres more air. As for at higher elevation (like for example at the top of mount everest) There is less air... The higher the elevation, the less air.
<em>~Hope this helped! :)</em>
739 degrees K equals 465.85 degrees Celcius.