Deceitful behavior or deceptive behavior?

My task is to give the correct form of the words in bracket in the following passage.

Honesty means fairness, justice, truth and sincerity. An honest person is upright in speech, thought and deed. He never thinks untruly or insincere. His thinking is always true, earnest and without any sort of (1_DECEIVE) __ behavior. Again he or she always speaks what is true even if it is bitter. He or she would never lie or cheat for the sake of any selfish end. On the other hand, he or she must stick to (2_TRUE) __ even at the cost of personal gains.

As for number 1, I think it would be deceptive but my teacher has said it is deceitful. And I would fill with truthfulness for number 2 but my teacher truth.
Please help me work out the answers and explain me why.

‘Deceitful’ is correct; it is the adjective meaning human pretense. ‘Truth’ is correct-- but it should read ‘the truth’. We stick to the truth if we possess truthfulness.