1. Having access to mesothermal and dry climates, mountains, and known for its beaches, Australia is an OK option, but it lacks tropical climates completely. Tanzania 2. has diverse cultures and languages, meso- and micro-thermal climates, and minor Europe alpine glaciers, but no tropical climates or deserts. Brazil
3. Having famous deserts, beaches, reefs, and even minor tropical areas makes California great option if you are willing to do without glaciers and alpine-like mountains.
4. Incredible rain forests and beaches are what stand out for , but the climate in nearly all tropical with little variety.
5. Possessing high mountains with glaciers, coastlines with beaches, deserts, savannas, has it all and spans highland, tropical, dry, and mesothermal climates with spicy food as well!
6. With the highest elevations on its continent, has amazing mountain landscapes with rapidly melting glaciers, tropical savannas for world-class safaris, beaches, and even deserts.

the independent variable, or the one that is intentionally manipulated is the speed.

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.

truck y has a greater velocity than truck x.