The concept of disk instability was developed to solve the problem that a. Jupiter-like planets migrate after formation. b. there was not enough gas in the Solar System to form Jupiter. c. the early solar nebula likely dispersed too soon to form Jupiter. d. Jupiter consists mostly of volatiles.

Planet formation is an intricate process that explains how celestial bodies like our Earth, Jupiter, and others in the Solar System came to be. This process primarily occurs in the protoplanetary disks surrounding young stars. Within these disks, dust and gas combine to form planetesimals, which are the building blocks of planets.
Over time, these planetesimals collide and stick together, gradually growing into larger planetary embryos and eventually full-sized planets. Two main theories explain how planets, especially gas giants, form: the core accretion model and the disk instability model.
The core accretion model suggests that gas and dust accumulate around a solid core over thousands to millions of years, while the disk instability model posits that gas giants like Jupiter form quickly due to gravitational instabilities within the disk.
This latter process bypasses the need for a prolonged accumulation phase, which is crucial when the surrounding gas in the disk might dissipate rapidly.

The solar nebula refers to the cloud of gas and dust from which our Solar System formed around 4.6 billion years ago. The nebular hypothesis suggests that gravitational collapse within a region of a large molecular cloud resulted in the formation of the Sun and surrounding planets.
As material within this nebula began to contract under gravity, it spun faster and flattened into a disk-like shape around the young Sun. This is the protoplanetary disk or solar nebula.
Within this environment, various processes led to the creation of planetesimals and eventually planets. The inner region, being hotter, gave rise to terrestrial planets like Earth, while the cooler outer regions led to the formation of gas giants such as Jupiter and Saturn.
Over time, interactions such as gravitational forces and radiation from the Sun led to the dispersion of the remaining gas and dust in the nebula. Hence, the timing of these dispersions is critical for models like disk instability, which relies on a quicker formation period for gas giants.

Gas giant planets, including Jupiter and Saturn in our Solar System, are massive planets primarily composed of hydrogen and helium. They differ from terrestrial planets in several significant ways.
Firstly, gas giants have much thicker atmospheres and lack solid surfaces, making them fundamentally different in structure from rocky planets like Earth or Mars.
The formation of gas giants is often explained by two models: core accretion and disk instability. Core accretion suggests that these giants began as solid cores that gradually attracted surrounding gas from the protoplanetary disk. However, this process can be too slow if the gas in the disk disperses quickly.
On the other hand, the disk instability model provides a faster formation pathway; it proposes that gravitational instabilities in the disk caused denser regions to collapse and form gas giants directly.
This model helps explain the presence of Jupiter and Saturn despite the relatively short lifespan of the solar nebula, as stated in option c from the exercise. Gas giants, therefore, play a crucial role in our understanding of planet formation and the history of our Solar System.