Which kind of wave would be observedusi outer space between planets, where there is very little matter

•an electromagnetic wave, such as an x-ray
•an electromagnetic wave, such as a sound wave
•a mechanical wave, such as an x-ray
•a mechanical wave, such as a sound wave

An electromagnetic wave such as x rays  wave would be observed outer space between planets, where there is very little matte

an electromagnetic wave such as x rays

Explanation:

Electromagnetic waves are the waves it can be observed in the outer space between the planets, the other waves such as the sound waves are the mechanical waves, which need the medium for its propagation.

There is no medium between the planets so there is an empty space for the propagation. Hence the sound waves do not pass through the medium.

The mechanical wave can have the material for the propagation. The electromagnetic waves can be used to transport the energy from one form to another. It does not require the material medium.

not only is it colder, it also becomes darker, less salty, and more dense.

the answer is sex-linked recessive.