This Contour Line problem with a graphical picture asked in each set this year ( both set 1 and set 2 papers) . In both sets questions are logical only .
No prior experience is required to solve them other than logical mind .
Now coming to this set 1 question,
given water level value is 525 m .
600 > P >550, 550 > Q > 525 , 500 >R > 450, 450 > S > 425 , 525 >T> 500
now to get submerged the value should be Less than 525
that condition is satisfied by R, S, and T only . Because P and Q have above 525 value.
so the answer is R, S, T -- which is option C .