Answer:
There is only one possible value for the quantity "c"
Step-by-step explanation:
There is only one possible value for the quantity "c". This is because the a,b,c and d represent number of moles in he balanced equation. And since the number of moles of a particular substance (atom or compound) in a balanced equation must be distinct, it (the substance) can only have one value. For example, consider the equation below
2C₂H₂ + 5O₂ ⇒ 4CO₂ + 2H₂O
It can be seen from the above equation that the individual number of moles are distinct and have just one possible value. And if C₂H₂ is A, O₂ is B, CO₂ is C and H₂O is D, then 4 is "c".
Thus, "c" is the number of moles for the substance "C" with just one possible value.