The farct to say " is the contrary" does not mean it is not good explanation. It means that the option is NOT true. And during the exam, under a pressure time condition, that is what you just need.

This is an exam that rewards the correct option NOT the best and beautiful reason why a question is correct or wrong.

Nonetheless I perfectly understand your position

The new theory proposes that:
1. A supernova triggers star formation from dense clouds of gas and dust.
2. The most massive star formed from this process evolves into a supernova, triggering another round of star formation.
3. This creates a chain of star-forming regions.
4. Many such chains in a rotating galaxy would result in a spiral distribution of stars, resembling observed spiral galaxies.

This theory contrasts with the widely accepted density wave theory, which suggests that a spiralshaped density wave compresses gas and dust to form stars in a spiral pattern.

Goal

We need to identify which option, if true, would most discredit the new theory. In other words, we're looking for a statement that undermines the key mechanisms or assumptions of the new theory.

Analyzing Each Option
Option A: The exact mechanism by which a star becomes a supernova is not yet completely known and may even differ for different stars.
- This suggests uncertainty about supernova mechanisms, but it doesn't directly contradict the new theory's chain reaction of supernovas triggering star formation. It's more of a general limitation in astrophysics, not specific to discrediting this theory.
- Impact on new theory: Minimal. Doesn't directly challenge the chain mechanism.

Option B: Chains of star-forming regions like those postulated in the new theory have been observed in the vicinity of dense clouds of gas and dust.

- This actually supports the new theory by providing observational evidence for the postulated chains.
- Impact on new theory: Strengthens it, so this is not discrediting.

Option C: The most massive stars formed from supernova explosions are unlikely to evolve into supernovas.
- The new theory relies on the most massive stars formed from a supernova evolving into supernovas themselves, continuing the chain. If these stars are unlikely to become supernovas, the chain reaction breaks down, and the theory's proposed mechanism fails to explain spiral galaxy structure.
- Impact on new theory: Directly undermines its core mechanism. This is a strong discrediting point.

Option D: Computer simulations of supernovas provide a poor picture of what occurs just before a supernova explosion.
- This critiques the accuracy of supernova simulations but doesn't directly address the chain reaction or the formation of spiral structures. The new theory's simulation reproduced spiral galaxies without assuming density waves, but this option doesn't challenge that result.
- Impact on new theory: Indirect and weak. Doesn't directly discredit the theory.

Option E: A density wave cannot compress clouds of gas and dust to a density high enough to create a star.
- This challenges the competing density wave theory, not the new theory. If anything, it might indirectly support the new theory by discrediting the alternative.
- Impact on new theory: None (it targets the other theory).

Why Option C is the Best Choice
The new theory's entire premise hinges on a chain reaction where:
1. Supernova triggers star formation.
2. The most massive of these new stars becomes a supernova, triggering more star formation.
3. This cycle repeats, creating chains that form spiral patterns.

If the most massive stars formed from supernovas are unlikely to become supernovas themselves (Option C), the chain reaction stops. No chains, no spiral structure from this mechanism. Thus, the theory falls apart.

Why Other Options Are Inferior
- A: Too vague; doesn't directly attack the theory.
- B: Supports the theory.
- D: Attacks simulations, not the theory's core logic.
- E: Attacks the competing theory, not this one.

Final Answer
Option C most discredits the new theory by undermining its essential chain-reaction mechanism.
Correct Answer: C