Q. Consider the following statements regarding the application of various elements and compounds:

1. Nickel acts as a catalyst in the hydrogenation process used for the production of margarine.
2. Galinstan, a liquid alloy consisting mainly of gallium, is used as a non-toxic alternative to mercury in thermometers.
3. Germanium-doped silica is primarily utilized in manufacturing optical fibers for high-speed internet connectivity.
4. Selenium is a common ingredient in anti-dandruff shampoos.

Which of the above statements is / are correct?
Answer: 1, 2, 3 and 4
Notes: All four statements are correct: Nickel catalyzes hydrogenation in margarine production; galinstan replaces toxic mercury in thermometers; germanium-doped silica is preferred for optical fiber production due to superior properties; and selenium is included in anti-dandruff shampoos primarily as antifungal agent. Each element or compound listed has widespread industrial or commercial use as stated.