The speed of sound depends upon
a) air density
b) temperature
c) pressure
d) humidity
so there can be different reasons that the instrument goes out of tune outside.
However in the given options the best is The speed of sound decreases with a decrease in temperature.
A. combustion
because carbon dioxide is the main product of burning carbon based fuels and combustion is the process of burning something
Positive or negative charge
A polyatomic ion is a cluster of covalently bonded atoms with a positive or negative charge that acts as a unit.
A polyatomic ion is a covalently bonded groups of atoms that acts as a single unit and has a positive or negative charge as a result of the formation of an ionic bond with another ion. An example of a polyatomic ion is hydroxide ion which has the chemical formula; OH− (has a charge of −1), and is made up of one oxygen atom and one hydrogen atom.
