Observations of the solar system support the nebular theory because

Because all the planets orbit the sun in the same direction, along a circular flattened disk.

Explanation:

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The observations that are made regarding the solar system supports the nebular theory because of the following reasons-

1) All the eight planets in the solar system move around the Sun in an anticlockwise direction. The moons of all these planets also orbit around them in the same direction, and the planets including the Sun rotate in the same way. This was believed that all these planets were formed from a disc of rock fragments rotting around the sun.

2) These planets are also observed to be configured from the disc of dust and gas particles such as hydrogen and helium, moving around the proto-sun. This hydrogen, helium gas is present only at the distant planets but are absent on the planets that are nearer to the sun. The Jovian planets are mainly composed of gases and are much bigger in size compared to the inner planets.

These are the observation that supported the nebular theory.

the answer to this question is 3.