The idea that 1+1=2 is so basic, some consider it a(n) _____ truth that doesn't need any proof.

Which word BEST COMPLETES this sentence?
IT was an AUTOMATIC belief because it was this.
  1. UNWIELDY
  2. SALUTARY
  3. FLOUT
  4. STRAITLACED
  5. AXIOMATIC
A B C D E
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