Principles of Accounting (Analyzing Transaction)  (a)Assuming that there
were no errors in journalizing or posting, what caused a credit
balance in the Cash account. (b) Is a credit balance in the cash
account currently an asset, a liability, owner's equity, a revenue, or
an expense? Why?

Looks like 3 questions to me.

It's only two questions (a) and (b)

So in (b) do you want to know what it is?  Or why?  Or both?

Both

(a)Assuming that there were no errors in journalizing or posting, what
caused a credit balance in the Cash account.

Simply put, your credits have exceeded your debits. Firstly, your
assumption is flawed.  There is no concept as negative cash.  The only
thing (a common mistake) is that if you performed a check run (paying
off accounts payable) without sufficient cash to cover those checks. 
The journal entry would be to credit cash and debit accounts payable
(reducing your liability).  In reality, all those checks would
eventually bounce without sufficient deposits (debits) to cover them. 
This sometimes happen when companies 'hold' checks cut for the reason,
giving the 'illusion' of negative cash.  This check run should be
reversed (debit cash, credit accounts payable) for financial statement
presentation purposes.

(b) Is a credit balance in the cash account currently an asset, a
liability, owner's equity, a revenue, or
an expense? Why?

See answer A.  It's an asset, but can never be less than zero.

The Company adhered to a policy of deposting all cash receipts in a
bank account and making all payments by check.  There are no
undeposited cash on hand.

Have you performed a bank reconciliation?

If so, get ready for bouncing checks.  You're bank account is overdrawn. :-(