Ecologist estimate the size and density of populations using quadrants and the

Yes it would be a physical change.

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

The molar mass of a substance is defined as the mass of 1 mol of that substance, expressed in grams per mole, and is equal to the mass of 6.022 × 10 23 atoms, molecules, or formula units of that substance.