Which structural feature of carbon dioxide contributes to its low melting point?

The answer for #3 is c but i don't know why

Which of these properties, used alone, would be least useful in identifying most minerals? a. color b. luster c. streak d. density

How many moles of sulfuric acid (h2so4) are needed to react completely with 6.8 moles of lithium hydroxide (lioh)? 2lioh + h2so4 → li2so4 + 2h2o a. 3.4 mol h2so4b. 6.8 mol h2so4 c. 10.2 mol h2so4 d. 13.6 mol h2so4