Real Easy Pick
(A) for children whose parents had also experienced such terrors in childhood it was
more likely that they would perceive their behaviour
as fundamentally different from their peers
(B) for children whose parents also experienced such terrors in childhood, they were
more likely
than other children prone to night terrors to perceive their behaviour
as fundamentally different from their peers'
(C) when children had parents who had also experienced such terrors in childhood it was
more likely for them to be perceiving their behaviour
as different from that of their peers'
(D) that children whose parents had also experienced such terrors in childhood were
more likely
than other children prone to night terrors to perceive their behaviour as fundamentally different from their peers'
(E) that when children had parents who had also experienced such terrors in childhood they were
more likely to be perceiving behavior that differed from their peers
We can easily eliminate A,C and E because more is followed by "as"... more should always be followed by "than".
From D and B
B can be eliminated because "for" introduces a sub-ordinate clause that has to be followed by a comma.
FANBOYS(For,And, Neither, But, Or,Yet,So) these boys should always be followed by a comma when joining the subordinate clause.