Undisclosed principal can require third party to fulfill the contract, unless
i. undisclosed principal was expressly excluded as a party in the written contract
ii. contract is negotiable instrument signed by agent with no indication of signing in a representative capacity
iii. performance of agent is personal to contract allowing third party to refuse principal's performance
iv. all of the above

iv. All of the above

Explanation:

An undisclosed principal is a principal where the third party is unknown about the principal of the contract. The third party also does not know that at the time of contract, the  agent is acting in the agency.

The undisclosed principal requires third party to fulfill the contract except :

i. Undisclosed principal was expressly excluded as a party in the written contract

ii. Contract is negotiable instrument signed by agent with no indication of signing in a representative capacity

iii. Performance of agent is personal to contract allowing third party to refuse principal's performance

Thus the answer is

iv. All of the above

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