Correct Answer:
B. 1
The foundational concept here is the definition of a logarithm. A logarithm answers the question: "To what power must the base be raised to get the number?" Mathematically, if logb(x) = y, then by = x.
B) 1 is the correct answer. When the number and the base are the same, for example, loga(a), we are asking what power 'a' must be raised to in order to get 'a'. The answer is always 1, because a1 = a.
A) 10 is incorrect; this is the base for common logarithms, not a general rule. C) -1 is incorrect; a-1 = 1/a, not 'a'. D) None of these is false because 1 is the correct answer.