Identify Which of the Following Items Would Likely Serve as a Source

Identify which of the following items would likely serve as a source document by marking an X in the appropriate column.The first one is done as an example.
$\begin{array}{|l|l|c|c|}\hline & & \text { Yes } & \text { No } \\\hline \text { Ex. } & \text { Credit card } & & \mathrm{X} \\\hline \text { a. } & \text { Credit card receipt } & & \\\hline \text { b. } & \text { Purchase order } & & \\\hline \text { c. } & \text { Invoice } & & \\\hline \text { d. } & \text { Balance sheet } & & \\\hline \text { e. } & \text { Bank statement } & & \\\hline \text { f. } & \text { Journal entry } & & \\\hline \text { g. } & \text { Electric power bill } & & \\\hline \text { h. } & \text { Employee earnings record } & & \\\hline\end{array}$