What is true about debt?

Under IRC $$166($a$),$ debt may be deductible if it becomes worthless in the taxable year

Business and nonbusiness bad debts are deductible under IRC $166($a$)$

Bona fide debt means that there is an enforceable obligation to repay debt especially if the borrower's venture is successful

A debt is considered worthless if it had value at the beginning of the year and has no value at any time thereafter