Examine the financials for Delta and United Airlines in $2021.$ Which firm was the most liquid in $2021?$a$.$ Delta, because its current ratio was $0\mathrm{.}76.$b$.$ United Airlines, because its current ratio was $1\mathrm{.}19$c$.$ United Airlines, because its cash balance was higher than Deltas.d$.$ Delta, because its revenues were higher than United Airlines.e$.$ United Airlines, because its total current liabilities were smaller than Deltas