Answer:
Option (1) is correct.
-10.6 and
are both independent of m and n. So they both are constant term.
Step-by-step explanation:
Consider the given expression, 
We have to find the constant term,
Constant term is a term that contain no variable and its value remain unchanged as it do not contain any variable with it.
For the given term it involves two variables m and n ,
So, for constant consider those term that do not contain m and n .
So , -10.6 and
are both independent of m and n. So they both are constant term.
Option (1) is correct.