How are the planes' contrail lines similar to clouds?

The contrail lines are the lines shaped clouds that are formed behind jet aircraft. It usually forms when the warm and humid air from the jet exhaust reacts with air that is comparatively of lower vapor pressure as well as temperature in the upper atmosphere. This combination of air is due to the instability that is caused by engine exhaust. These lines are also known as the condensation trail. They are mainly composed of water which is typically in the form of small ice crystals.

These contrails lines are similar to the clouds as both show similar characteristics. They are similar in appearance as well as in terms of composition. Both are comprised of tiny water droplets and frozen ice crystals.

i believe it is-

d.) gravity pulled particles of dust and gas together to form planets.