According to the conditions, the equation (x-12) 2 = (x-4) * (x-18) can be listed to find X, that is, a 1, and then the available D can be calculated.

5. From the condition, we can get lnx*lny= 1/4, and from the basic inequality, we can get lnx*lny when lnx+lny is greater than or equal to 2.

That is, lnx+lny is greater than or equal to 1, that is, ln(x*y) is greater than or equal to 1, so b is selected.