Topic analysis: This topic is the application of monotonicity in the properties of logarithmic functions. The application of monotonicity is generally to compare sizes, solve inequalities and find the maximum value.

But this topic also includes the flexible application of logarithmic operation.

Problem solving: First of all, you can see a> 1 from the diagram and get the value of f(0).

- 1 & lt； Log a (b) <; 0

Then 0

Left-1 to be deformed: it should be noted that the deformation of 1 should be flexible logarithmically, and 1 can usually be written as: log a (a).

Then-1 can be written as -loga (a) = loga (1/a).

According to a> 1, monotonically increasing, and then1/a.

A: A.