Question

1. what is the main reason the inner core of the earth is solid? it is cooler than the outer core. it has a higher concentration of silicon and aluminum. immense pressure keeps it solid despite high temperatures. it contains less iron and nickel than the outer core.

Explanation:

To determine the main reason the Earth's inner core is solid, we analyze each option:

• Option 1: The inner core is actually very hot (similar to the outer core in temperature range), so "cooler" is incorrect.
• Option 2: The Earth's core is mainly iron and nickel, not silicon and aluminum (which are more abundant in the crust), so this is wrong.
• Option 3: The inner core is under extreme pressure from the overlying layers. Even though temperatures are extremely high (hot enough to melt it under normal pressure), the immense pressure forces the iron - nickel alloy to remain in a solid state. This matches the scientific understanding.
• Option 4: The inner core has a similar (or slightly different but not "less") concentration of iron and nickel compared to the outer core. The outer core is liquid due to lower pressure, not less iron/nickel.

Answer:

C. Immense pressure keeps it solid despite high temperatures. (Note: Assuming the options are labeled A - D with A being "It is cooler...", B "It has a higher...", C "Immense pressure...", D "It contains less...")