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1992 AMC 12 Question 4

AMC12 · 1992 AMC 12

Question 4

If $a,$ $b,$ and $c$ are positive integers and $a$ and $b$ are odd, then $3^a+(b-1)^2c$ is
  1. odd for all choices of $c$
  2. even for all choices of $c$
  3. odd if $c$ is even; even if $c$ is odd
  4. odd if $c$ is odd; even if $c$ is even
  5. odd if $c$ is not a multiple of $3$; even if $c$ is a
    multiple of $3$