One example of an ionic compound is

f2
co2
hbr
mgcl2

MgCl2 because it is the only option in which a metal appears with a nonmetal. In this case, the metal transfers electrons to the nonmental because the metal has a lower ionization energy.

Looking at choices, Mg has a positive charge in the compound so it is a metal and Cl2 is a non-metal (negative charge), so it is sonic since they contain a metal and non metal, where metal transfers electrons to non-metal thus having a positive charge, and non-metal has negative

MgCl2

Butterfly wingspan is 7.7

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