What is the true solution to in 20+in 5=2 in x?

"true solution?"  

ln 20  +  ln 5  =  2 ln x can be re-written as

ln (20)(5)  = ln x^2.  We can drop the "ln" operator:

100=x^2                   which yields x=10 and x=-10.  The negative result must be discarded, since 2 ln (-10) is undefined.

x=10 (answer)  

I’d say letter a..