When you multiply it out by hand to get
2678 × 97 = 259766
you place the decimal point in the answer by counting the number of decimal places of the multiplicands.
2.678 has 3 decimal places
9.7 has 1 decimal place
The product of these numbers will have 3+1 = 4 decimal places, so will look like
B) 25.9766
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You can also get there by considering that the product is about 10×2.6, so is about 26. That will tell you the decimal point goes after the first two left-most digits.