Step 1: Examine Option A - "Indispensable''
"Indispensable'' is correctly spelled. It means absolutely necessary.
Step 2: Examine Option B - "Embarass''
"Embarass'' is incorrect. The correct spelling is "embarrass'' — with two "r''s and two "s''s.
Step 3: Examine Option C - "Discrepancy''
"Discrepancy'' is correctly spelled. It means a lack of compatibility or similarity.
Step 4: Examine Option D - "Acquire''
"Acquire'' is correctly spelled. It means to gain or obtain something.
So, the incorrect spelling is Option B: "Embarass'' $\rightarrow$ "Embarrass''.