B. Sand.
Sand would definitely increase friction because of the roughness of it surface. When its surface comes with another rough surface it would tend to increase friction. All other options given tend to reduce friction one way or the other.
The best substance to heat up the fastest would be blue fire
This is a reduction half-reaction. Initially, gold exists as

, and after the reaction, it has been converted to elemental gold. To make this possible, three electrons must be added to <span>

. This fits within the definition of reduction reactions, where the reactant gains electrons in the reaction.</span>
The result is the sound will be louder. This is due to the high amount of energy in the sounds.
9 g of hydrogen - 42 g of nitrogen
5 g of hydrogen - x g of nitrogen

The mass of nitrogen in the second sample is 23.33 g.