Accessing instantiated variable in call predicate

Hi to all,

i've just started using 'call' predicate, and i was wondering how i can
access the variable that are instantiated in the predicate that is passed
to the 'call' predicate as variable.
For example, this is my case. I've this predicate:

getAtom(Sent) :- s(LogicForm,Sent,[]), call(LogicForm).

Now, LogicForm indeed represent the logic form of the analyzed sentence.
Through the predicate 'call', I execute the query represented by the logic
form on my KB. Again, the logic form represent a predicate, as:

to(chair,A)

where A is the variable that will be instantiated with the value I need to
retrieve.
Then, how can i access that value starting from the getAtom predicate? All
that I can get is the instatiation of the variable LogicForm, as

LogicForm = to(chair, chair_1)

while* *I want to get just the chair_1 atom instance.

Thank you.
EB
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