Which of the following statements are correct
(i) Positron is predicted by Dirac and discovered by Anderson
(ii) Liquid drop model of nucleus by Bohr and Wheeler is developed
(iii) Carbon cycle was proposed by Bethe
(iv) Fission reaction is first observed Otto Hahn and Strass man

Options

A. All are true
B. Only i, ii & iv are true
C. Only i, iii & iv are true
D. Only iii & iv are true

Answer

To determine which statements are correct, let's analyze each one step by step.

**Step 1: Analyze Statement (i)**
- Statement: "Positron is predicted by Dirac and discovered by Anderson."
- Explanation: The positron, which is the antiparticle of the electron, was indeed predicted by the physicist Paul Dirac in 1928 as a consequence of his theory of quantum mechanics and special relativity. It was later discovered by Carl D. Anderson in 1932.
- Conclusion: This statement is **correct**.

**Step 2: Analyze Statement (ii)**
- Statement: "Liquid drop model of nucleus by Bohr and Wheeler is developed."
- Explanation: The liquid drop model of the nucleus is a model that describes the nucleus as a collection of nucleons (protons and neutrons) similar to a drop of liquid. However, this model was primarily developed by George Gamow, not by Bohr and Wheeler.
- Conclusion: This statement is **incorrect**.

**Step 3: Analyze Statement (iii)**
- Statement: "Carbon cycle was proposed by Bethe."
- Explanation: The carbon cycle, which describes the fusion processes that occur in stars, was indeed proposed by Hans Bethe in the 1930s. This process explains how stars convert hydrogen into helium and other heavier elements.
- Conclusion: This statement is **correct**.

**Step 4: Analyze Statement (iv)**
- Statement: "Fission reaction is first observed by Otto Hahn and Strassman."
- Explanation: The discovery of nuclear fission was indeed made by Otto Hahn and Fritz Strassmann in 1938. They conducted experiments that led to the identification of barium as a product of uranium bombardment, which was a pivotal moment in nuclear physics.
- Conclusion: This statement is **correct**.

**Final Conclusion:**
Based on the analysis:
- Statement (i) is correct.
- Statement (ii) is incorrect.
- Statement (iii) is correct.
- Statement (iv) is correct.

Thus, the correct statements are (i), (iii), and (iv).

### Final Answer:
The correct statements are: (i), (iii), and (iv).

---