The correct answer is D. Unable to pay his debts.
An insolvent person is a person who is unable to pay his debts. This means that they have more debts than they have assets to cover them. Insolvent people may be forced to sell their assets to pay off their debts, or they may file for bankruptcy.
Option A is incorrect because it is possible for someone to be able to pay their daily expenses but still be insolvent. For example, someone who has a lot of credit card debt may be able to make their minimum payments each month, but they may still be unable to pay off the debt in full.
Option B is incorrect because it is possible for someone to pay their taxes but still be insolvent. For example, someone who has a lot of medical bills may be able to pay their taxes, but they may still be unable to pay off their medical debt.
Option C is incorrect because it is possible for someone to take out a loan and pay it back, even if they are insolvent. For example, someone who takes out a student loan may be able to pay it back over time, even if they are struggling to make ends meet in the short term.