Question

1. limestone is made mostly of calcium carbonate. heating limestone and then adding water produces calcium hydroxide, which is called cement. cement can be poured into forms to make such things as sidewalks and building foundations. as cement hardens, another reaction takes place, and the calcium hydroxide turns back into calcium carbonate. hardened cement is called concrete. why is concrete more useful than limestone?

a. limestone is not a renewable resource.
b. limestone is hard to get out of the ground.
c. concrete can be poured to into different shapes.
d. concrete is completely pure calcium carbonate.

Explanation:

The text states that cement (which becomes concrete) can be poured into forms. This implies that concrete can take different shapes as per the forms. Option C aligns with this as it mentions concrete can be poured into different shapes. Option A about limestone not being renewable is not relevant to why concrete is more useful. Option B about limestone being hard to get is not mentioned. Option D is incorrect as concrete is hardened cement (calcium hydroxide turning back to calcium carbonate but not completely pure as per the given info).

Answer:

C. Concrete can be poured to into different shapes.