1. Who can stop payment on an item?

Any owner of the account.
Any person authorized to draw on the account.
Only the person who signed the original item.

2. If a check is made out to Carly Simon and James Taylor and one name is simply typed above the other name, who can negotiate and cash the check?

Either one of them because it's payable ambiguously.
Only both of them together. Each must endorse it.
A court would have to decide.

3.If a check shows two different amounts, one in words and one in numbers, it is:

It is risky to pay it.
It is not properly payable.
Properly payable for the amount written in words.

4. If a check does not state a payee, it is considered:

payable to bearer
an incomplete instrument
not properly payable

5. "Alteration", as defined in the UCC, includes ___________________________ or (ii) an unauthorized addition of words or numbers or other change to an incomplete instrument relating to the obligation of a party.

a change to a check or draft, but it must be both unauthorized and purport to modify in some respect the obligation of a party
any change to a check or draft
a check signed by a party whose signature is not on the signature card