Which one is different from the other three?

If '+' means '×', '−' means '÷', '×' means '+' and '÷' means '−', then which one of the following equations is correct?

If "No scientists are philosophers" is true, which one of the following propositions is true?

Which one of the following years will have the same calender as of 2009?

What is the digit in the unit place of the number 1^1 × 3^3 × 5^5 × 7^7 × 9^9?

Which term is wrong in the following series? 8, 13, 21, 32, 47, 63, 83