Answer:
if f⊥m and m⊥n then f⊥n, option C is correct.
Explanation:
Given that in a plane if line f is perpendicular to line m
we have to choose the condition which results f⊥n.
f⊥m and required result we want is f⊥n
By transitivity property
if a relates with b and b relates with c then a also related with c
Here, relation of a and b given i.e f⊥m and relation of a and c given i.e f⊥n
we have to find a relation between m and n so that f⊥n holds
By transitivity law,
if f⊥m and m⊥n then f⊥n
Hence, option C is correct.