10⁶ is 100 times the size of 10⁴.
The wording "cell b is 100 times greater than cell a" is ambiguous, as it isn't clear what property of the cell is being referred to.
If we assume the reference is to the diameter of the cell, then choice B) is appropriate (b is 100 times a).
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We also consider the wording "times greater than" to be ambiguous. If b is 100 more than a, we say b is 100 greater than a. If a=1 and b=100, we would say b is 99 greater than a. In this case, b also happens to be 100 times as great as a, but greater than a by only 99 times the size of a.
