Final answer:
Both 'using two sets of books of accounts' and 'non-issuance of commercial invoice' can be considered forms of tax evasion, as they involve intentional manipulation or concealment of taxable financial activities.
Step-by-step explanation:
Options a and b, namely, using two sets of books of accounts and non-issuance of commercial invoice, could both be considered as tax evasion. Tax evasion is the illegal act of deliberately avoiding to pay true tax liabilities. By having two sets of books, a person might underreport income or overreport expenses leading to an artificially low tax bill. Non-issuance of commercial invoices can also be a way to evade taxes, as it may hide the undergoing of taxable transactions. Hence the correct answer to your question is c. Both a and b.
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