Make the question "mandatory".
You see your requirement "at least one answer per row" is exactly what mandatory means in this case (each row is answered)
I do not see any reason to have it "non mandatory" as your previous questions are mandatory.
Otherwise you can use a not complicated, but long "question validation equation".
Like this (either it was not selected in P36a or even not displayed in P36a or the number of answers is greater then 0)
(is_empty(P36a_1.NAOK) or count(self.sq_1.NAOK)>0) and (is_empty(P36a_2.NAOK) or count(self.sq_2.NAOK)>0) and (is_empty(P36a_3.NAOK) or count(self.sq_3.NAOK)>0) and (is_empty(P36a_4.NAOK) or count(self.sq_4.NAOK)>0) and (is_empty(P36a_5.NAOK) or count(self.sq_5.NAOK)>0) and (is_empty(P36a_6.NAOK) or count(self.sq_6.NAOK)>0) and (is_empty(P36a_7.NAOK) or count(self.sq_7.NAOK)>0) and (is_empty(P36a_8.NAOK) or count(self.sq_8.NAOK)>0) and (is_empty(P36a_9.NAOK) or count(self.sq_9.NAOK)>0) and (is_empty(P36a_A.NAOK) or count(self.sq_A.NAOK)>0) and (is_empty(P36a_B.NAOK) or count(self.sq_B.NAOK)>0)
To be able to use the ".self" variable I changed the codes "10" and "11" to "A" and "B".
Otherwise "self.sq_1" would affect both codes "1", "10" and "11" (all contain a "1").
On the other side you may change the codes to "01", "02", ... "10"
Now "self.sq_01" is different from "self.sq_10"
Furthermore I changed the x-axis codes to "a", "b" , "c" for the same reasons; no interference with "self.sq_1"
Joffm