Concept:
The objective of this question is to identify the correct spelling of the common English adjective that means "impossible to believe" or "extraordinary".
Let us break down the word etymologically:
• Prefix: in- (meaning *not*).
• Root: cred (from the Latin *credere*, meaning *to believe* or *trust*, as seen in words like *credit*, *credible*, or *creed*).
• Suffix: -ible (a standard suffix meaning *capable of* or *suitable for*).
Combining these components yields: i-n-c-r-e-d-i-b-l-e.
Let us examine why the other choices are incorrect variations:
• Option (A) incradible: Incorrectly replaces the 'e' in the root with an 'a'.
• Option (C) ingredable: Confuses the 'c' with a 'g' and uses the incorrect suffix "-able".
• Option (D) ingredible: Confuses the root consonant 'c' with a 'g'.
Therefore, Option (B) is the only correctly spelled variation.