Answer:
B. A number subtracted from 7 .
Explanation:
The given choices are
A. 7 less than a number
B. A number subtracted from 7
C. A number minus 7
D. The difference between a number and 7
The given expression is:

Remeber, variabels are called "a number" indicating its variability, because they are unknown values.
So, this expression can be written as: "7 less than a numer" or "the difference between a number and 7" or "a number minus seven".
Therefore, among the options, choice B doesn't represents the given expression, because "a number subtracted from 7" is equivalent to
which is not the case here.
So, the right answer is B.