The correct answer is option 4: Universal Basic Income (UBI). Universal Basic Income is an alternative approach to subsidies in poverty alleviation. It is a social welfare system where every individual, regardless of their income or employment status, receives a regular unconditional income from the government.

Option 1, Union Basic Income, is not the correct answer. It is not a commonly used term and does not accurately represent the concept of UBI.

Option 2, Undefined Basic Income, is also not the correct answer. UBI is a well-defined concept and has been extensively studied and debated.

Option 3, Unconditional Basic Income, is a close synonym for UBI, but it is not the commonly used term. While the term "unconditional" is used to describe UBI because it is not means-tested or tied to any work requirements, the term "universal" is more commonly used to indicate that the income is provided to everyone, regardless of their circumstances.

Therefore, the correct answer is option 4: Universal Basic Income.