A researcher studying organic compounds has found that five different molecules. T, W, X, Y and Z form chains according to the following rules :
A chain consists of three or more molecules, though the molecules in the chain are not necessarily different.
T is never found on either end of a chain.
If W appears in a chain, it appears more than once.
X is never found next to y in a chain.
W is never found on the end of a chain
unless Z is found somewhere in the chain.
If Y appears in a chain, Z appears also,
The chain W W T Y Z X can be changed into another chain by carrying out any one of the following EXCEPT
Solution
A. A new chain can be formed by replacing Y with T.
B. A new valid chain can be formed by replacing Y with X.
C. The chain will be invalid if X is replaced by T because T can not appear on the end.
D. A valid chain can be formed by exchanging T and Z.
Thus, the answer is Option C.
