Answer:
Ethylene glycol
HOCH₂CH₂OH
Explanation:
For the molecules in the question, the viscosity will rise with the number of hydrogen bonds that can be formed.
A hydrogen bond is a week physical bond which is formed when hydrogen is found between atoms with high electronegativity (oxygen, nitrogen, fluorine):
O-H ··· O, N-H ··· O, N-H ··· O, O-H ··· N, F-H ··· F and so on.
Here we have have two compounds that can form hydrogen bonds (between themselves):
C) ethanol and D) ethylene glycol
Ethylene glycol have more hydroxide groups (-OH) than the ethanol so it will form more hydrogen bonds thus increasing its viscosity.
