For each structure, 1. star 1*2 any asymmetric carbon atoms. 2. label each asymmetric carbon as (r) or (s). 3. draw any internal mirror planes of symmetry. 4. label the structure as chiral or achiral. 5. label any meso structures.

Combustion is the act or process of burning. therefore, i believe the answer is  a: burning wood. 

Answer is: the equilibrium  shifts toward the reactants, to the left side of chemical reaction.it is because lead(ii) nitrate dissociates in water: pb(no₃)₂ → pb²⁺(aq) + 2no₃⁻(aq).according to lechatelier's principle, the position of equilibrium moves to counteract thechange (more lead cations, common ion), the position of equilibrium will move so that the concentration ofproducts decrease and concentration of reactants of chemical reaction increase.read more on -